Display device and operating method thereof

ABSTRACT

A display device that achieves both high detection sensitivity of the touch sensor unit and smooth input on the touch sensor unit is provided. A method for driving a display device includes a first period and a second period. The display device includes pixels, a gate driver, and a touch sensor unit. The touch sensor unit detects a touch in the first period and stops detecting a touch in the second period. The gate driver supplies signals to some of the pixels and does not supply signals to the other pixels in the second period.

TECHNICAL FIELD

One embodiment of the present invention relates to a display device anda method for operating the display device. Furthermore, one embodimentof the present invention relates to a semiconductor device.

Note that one embodiment of the present invention is not limited to theabove technical field. The technical field of the invention disclosed inthis specification and the like relates to an object, a method, or amanufacturing method. Furthermore, one embodiment of the presentinvention relates to a process, a machine, manufacture, or a compositionof matter.

Specifically, examples of the technical field of one embodiment of thepresent invention disclosed in this specification and the like include adisplay device, a semiconductor device, an electronic device, a methodfor driving any of them, and a method for manufacturing any of them. Inthis specification and the like, a semiconductor device generally meansa device that can function by utilizing semiconductor characteristics.For example, an integrated circuit, a chip including an integratedcircuit, an electronic component including a packaged chip, and anelectronic device including an integrated circuit are examples of asemiconductor device.

BACKGROUND ART

A display device in which a display unit and a touch sensor unit arecombined is used. A detection region of the touch sensor unit overlapswith a display region of the display unit, so that the display devicedisplays an image in the display region and can obtain information ofthe position in the display region indicated by a user. The userperforms input with a finger, a stylus, or the like.

A transistor including an oxide semiconductor can be used for a pixel ofthe display unit. A transistor including an oxide semiconductor exhibitsan extremely low off-state current; hence, the frequency of refreshoperations when a still image is displayed by the display unit can bereduced. In this specification and the like, the technique for reducingthe frequency of refresh operations is referred to as idling stop or IDSdriving (Patent Document 1 and Patent Document 2). The IDS driving canreduce power consumption of the display unit.

PATENT DOCUMENT

-   [Patent Document 1] Japanese Published Patent Application No.    2011-141522-   [Patent Document 2] Japanese Published Patent Application No.    2011-141524

DISCLOSURE OF INVENTION

Although the frequency of image rewriting by the display unit isgenerally about 60 times per second (in other words, the frame frequencyis 60 Hz), detection operation by the touch sensor unit needs to beperformed 80 times or more per second, preferably 100 times or more persecond because smooth input such as handwriting input is required forthe touch sensor unit.

In the case where the touch sensor unit performs detection operation attiming when the display unit rewrites an image, the detectionsensitivity of the touch sensor unit deteriorates by the influence ofnoise. An object of one embodiment of the present invention is toprovide a display device that achieves both the detection sensitivity ofthe touch sensor unit and smooth input on the touch sensor unit.

An object of one embodiment of the present invention is to provide anovel display device. Another object of one embodiment of the presentinvention is to provide a novel driving method that achieves both thedetection sensitivity of the touch sensor unit and smooth input on thetouch sensor unit. Another object of one embodiment of the presentinvention is to provide an electronic device using the novel displaydevice.

Note that one embodiment of the present invention does not necessarilyachieve all the objects listed above and only needs to achieve at leastone of the objects. The description of the above objects does notpreclude the existence of other objects. Other objects will be apparentfrom and can be derived from the description of the specification, thedrawings, the claims, and the like.

One embodiment of the present invention is a method for driving adisplay device including pixels, a gate driver, and a touch sensor unit.The display device includes a first period and a second period. Thetouch sensor unit detects a touch in the first period and stopsdetecting a touch in the second period. The gate driver supplies signalsto some of the pixels and does not supply signals to the other pixels inthe second period.

In the above embodiment, the first period and the second period are inone frame.

In the above embodiment, the pixels each include a transistor includinga metal oxide in a channel formation region.

One embodiment of the present invention is a method for driving adisplay device including pixels, a gate driver, and a touch sensor unit.The display device includes a first period and a second period. Thetouch sensor unit detects a touch in the first period and stopsdetecting a touch in the second period. The pixel includes a reflectiveelement and a light-emitting element. The gate driver supplies signalsto some of the pixels and does not supply signals to the other pixels inthe second period.

In the above embodiment, the first period and the second period are inone frame.

In the above embodiment, the pixels each include a transistor includinga metal oxide in a channel formation region.

One embodiment of the present invention is a display device including anapplication processor, a display unit, and a touch sensor unit. Theapplication processor is configured to control the display unit and thetouch sensor unit in a first period and a second period. The firstperiod is a period in which the display unit rewrites an image and thesecond period is a period in which the touch sensor unit performsdetection. The display unit includes a first mode in which an image inan entire display region is rewritten, a second mode in which an imagein part of a display region is rewritten, and a third mode in which animage in an entire display region is not rewritten. The second period ofthe second mode and the third mode is longer than the second period ofthe first mode.

One embodiment of the present invention can provide a novel displaydevice. Another embodiment of the present invention can provide adisplay device that achieves both the detection sensitivity of a touchsensor unit and smooth input on the touch sensor unit.

Another embodiment of the present invention can provide a novel drivingmethod that achieves both the detection sensitivity of a touch sensorunit and smooth input on the touch sensor unit. Another embodiment ofthe present invention can provide an electronic device using the noveldisplay device.

Note that the effects of one embodiment of the present invention are notlimited to the effects listed above. The effects listed above do notpreclude the existence of other effects. The other effects are the onesthat are not described above and will be described below. The othereffects will be apparent from and can be derived from the description ofthe specification, the drawings, and the like by those skilled in theart. One embodiment of the present invention has at least one of theeffects listed above and the other effects. Accordingly, one embodimentof the present invention does not have the effects listed above in somecases.

BRIEF DESCRIPTION OF DRAWINGS

In the accompanying drawings:

FIG. 1 is a block diagram illustrating a structure example of a displaydevice;

FIG. 2 is a block diagram illustrating a structure example of a touchsensor unit;

FIG. 3 is a block diagram illustrating a structure example of a displayunit;

FIGS. 4A to 4C are circuit diagrams illustrating a configuration exampleof a gate driver;

FIGS. 5A and 5B are circuit diagrams each illustrating a configurationexample of a shift register;

FIG. 6 is a timing chart showing an operation example of a gate driver;

FIG. 7 is a timing chart showing an operation example of normal display;

FIG. 8 is an external view illustrating an embodiment and a usageexample of a tablet information terminal;

FIG. 9 is a timing chart showing an operation example of partial IDSdriving;

FIG. 10 is a timing chart showing an operation example of partial IDSdriving;

FIG. 11 is a timing chart showing an operation example of IDS driving;

FIG. 12 is a flow chart showing an operation example of an electronicdevice;

FIGS. 13A to 13D illustrate a usage example of an information terminaland states of signals input to a gate driver;

FIG. 14 is a flow chart showing an operation example of an informationterminal;

FIGS. 15A to 15D illustrate a usage example of an information terminaland states of signals input to a gate driver (in the case of alight-emitting element);

FIGS. 16A to 16C are a top view and projection views illustrating astructure example of a touch sensor unit;

FIGS. 17A and 17B are a top view and a projection view illustrating astructure example of a touch sensor unit;

FIG. 18 is a block diagram illustrating a structure example of a displaydevice;

FIG. 19 is a circuit diagram illustrating a structure example of apixel;

FIG. 20 is a circuit diagram illustrating a structure example of apixel;

FIGS. 21A and 21B are a circuit diagram illustrating a structure exampleof a pixel and a timing chart;

FIGS. 22A to 22D are schematic cross-sectional views each illustrating astructure example of a display device;

FIGS. 23A and 23B are schematic cross-sectional views each illustratinga structure example of a display device;

FIGS. 24A and 24B are schematic cross-sectional views each illustratinga structure example of a display device;

FIGS. 25A and 25B are schematic cross-sectional views each illustratinga structure example of a display device;

FIGS. 26A to 26C are schematic cross-sectional views each illustrating astructure example of a display device;

FIG. 27 is a cross-sectional view illustrating a structure example of adisplay device;

FIG. 28 is a cross-sectional view illustrating a structure example of adisplay device;

FIGS. 29A and 29B are block diagrams each illustrating a structureexample of a source driver;

FIGS. 30A to 30D are schematic views illustrating a structure of a pixelof a display unit;

FIGS. 31A and 31B are cross-sectional views illustrating a structure ofa pixel of a display unit;

FIGS. 32A to 32C are top views and a cross-sectional view illustrating astructure of a display unit;

FIGS. 33A to 33C are cross-sectional views illustrating a structure of adisplay unit;

FIG. 34 is a cross-sectional view illustrating a structure of a displayunit;

FIGS. 35A and 35B are bottom views illustrating a structure of a pixelof a display unit;

FIG. 36 is a circuit diagram illustrating a pixel circuit of a displayunit;

FIGS. 37A to 37C are top views each illustrating a structure of areflective film of a display unit;

FIGS. 38A and 38B are top views illustrating pixels and subpixels of adisplay unit and an external view of a conductive film;

FIGS. 39A and 39B are cross-sectional views illustrating a structure ofa pixel of a display unit;

FIGS. 40A to 40E each illustrate a structure of a data processingdevice;

FIGS. 41A to 41E each illustrate a structure of a data processingdevice;

FIG. 42 is a schematic view illustrating an example of a display unit;

FIGS. 43A to 43F are photographs showing the appearance of a fabricateddisplay unit;

FIGS. 44A and 44B are graphs showing power consumption of a fabricateddisplay unit;

FIGS. 45A to 45E are photographs showing the appearance of a fabricateddisplay unit; and

FIGS. 46A and 46B are graphs showing power consumption of a fabricateddisplay unit.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, embodiments will be described with reference to drawings.However, the embodiments can be implemented with various modes. It willbe readily appreciated by those skilled in the art that modes anddetails can be changed in various ways without departing from the spiritand scope of the present invention. Thus, the present invention shouldnot be interpreted as being limited to the following description of theembodiments. Any of the embodiments described below can be combined asappropriate.

A display device described in an embodiment is composed of a displayunit, a touch sensor unit, and the like. Therefore, the display deviceis also referred to as a semiconductor device, an electronic device, orthe like in some cases.

In the drawings and the like, the size, the layer thickness, the region,or the like is sometimes exaggerated for clarity, and thus is notlimited to the illustrated scale. Note that drawings are schematic viewsof ideal examples, and the embodiments of the present invention are notlimited to the shape, the value, or the like illustrated in thedrawings.

In the drawings and the like, the same elements, elements having similarfunctions, elements formed of the same material, elements formed at thesame time, and the like are sometimes denoted by the same referencenumerals, and the description thereof is not repeated in some cases.

In this specification and the like, the terms “film” and “layer” can beinterchanged with each other. For example, the term “conductive layer”can be changed into the term “conductive film” in some cases. Also, theterm “insulating film” can be changed into the term “insulating layer”in some cases.

In this specification and the like, the terms for describing arrangementsuch as “above” and “below” do not necessarily mean “directly above” and“directly below”, respectively, in the description of a physicalrelationship between components. For example, the expression “a gateelectrode over a gate insulating layer” can mean the case where there isan additional component between the gate insulating layer and the gateelectrode. In this specification and the like, the term “parallel”indicates that the angle formed between two straight lines is greaterthan or equal to −10° and less than or equal to 10°, and accordinglyalso includes the case where the angle is greater than or equal to −5°and less than or equal to 5°. The term “perpendicular” indicates thatthe angle formed between two straight lines is greater than or equal to80° and less than or equal to 100°, and accordingly also includes thecase where the angle is greater than or equal to 85° and less than orequal to 95°.

In this specification and the like, ordinal numbers such as “first”,“second”, and “third” are used in order to avoid confusion amongcomponents, and the terms do not limit the components numerically.

In this specification and the like, the term “electrically connected”includes the case where components are connected through an objecthaving any electric function. There is no particular limitation on the“object having any electric function” as long as electric signals can betransmitted and received between components that are connected throughthe object. Examples of an “object having any electric function” are aswitching element such as a transistor, a resistor, an inductor, acapacitor, and elements with a variety of functions as well as anelectrode and a wiring.

In this specification and the like, the term “voltage” often refers to adifference between a given potential and a reference potential (e.g., aground potential). Accordingly, voltage, potential, and potentialdifference can also be referred to as potential, voltage, and voltagedifference, respectively.

In this specification and the like, a transistor is an element having atleast three terminals: a gate, a drain, and a source. The transistor hasa channel region between a drain (a drain terminal, a drain region, or adrain electrode) and a source (a source terminal, a source region, or asource electrode), and current can flow between the source and the drainthrough the channel region. Note that in this specification and thelike, a channel region refers to a region through which current mainlyflows.

Furthermore, functions of a source and a drain might be switched whentransistors having different polarities are employed or a direction ofcurrent flow is changed in circuit operation, for example. Therefore,the terms “source” and “drain” can be switched in this specification andthe like.

Unless otherwise specified, off-state current in this specification andthe like refers to drain current of a transistor in an off state (alsoreferred to as a non-conducting state and a cutoff state). Unlessotherwise specified, the off state of an n-channel transistor means thata gate voltage with respect to a source voltage (V_(gs)) is lower thanthe threshold voltage (V_(th)), and the off state of a p-channeltransistor means that V_(gs) is higher than V_(th). That is, theoff-state current of an n-channel transistor sometimes refers to a draincurrent that flows when the gate voltage with respect to the sourcevoltage V_(gs) is lower than the threshold voltage V_(th).

In the above description of off-state current, a drain may be replacedwith a source. That is, the off-state current sometimes refers tocurrent that flows through a source of a transistor in the off state.

In this specification and the like, the term “leakage current” sometimesexpresses the same meaning as “off-state current”. In this specificationand the like, the off-state current sometimes refers to a current thatflows between a source and a drain when a transistor is in the offstate.

In this specification and the like, a metal oxide means an oxide ofmetal in a broad sense. Metal oxides are classified into an oxideinsulator, an oxide conductor (including a transparent oxide conductor),an oxide semiconductor (also simply referred to as an OS), and the like.For example, a metal oxide used in an active layer of a transistor iscalled an oxide semiconductor in some cases. That is to say, a metaloxide that has at least one of an amplifying function, a rectifyingfunction, and a switching function can be called a metal oxidesemiconductor, or OS for short. An OS transistor or an OS FET refers toa transistor including a metal oxide or an oxide semiconductor.

(Embodiment 1)

In this embodiment, a display device including a display unit and atouch sensor unit is described. In particular, the relation betweenimage rewriting operation by the display unit and detection operation bythe touch sensor unit is described.

«Display Device»

FIG. 1 is a block diagram illustrating a structure example of a displaydevice. A display device 50 includes a display unit 60, a touch sensorunit 70, and an application processor 80.

<Display Unit>

The display unit 60 includes a pixel array 61, a gate driver 62, a gatedriver 63, and a source driver IC 64.

The pixel array 61 includes a plurality of pixels 10, and each pixel 10is an active element driven by a transistor. The pixel array 61 has afunction of forming a display region of the display unit 60 anddisplaying an image. A more specific structure example of the pixelarray 61 is described later.

The gate driver 62 and the gate driver 63 have a function of driving agate line for selecting the pixel 10. Only one of the gate driver 62 andthe gate driver 63 may be provided. Although FIG. 1 illustrates anexample in which the gate driver 62 and the gate driver 63 are providedtogether with the pixel array 61 over the same substrate, the gatedriver 62 and the gate driver 63 can be dedicated ICs.

The source driver IC 64 has a function of driving a source linesupplying a data signal to the pixel 10. Although the source driver IC64 is mounted by a chip on glass (COG) method here, there is noparticular limitation on the mounting method, and a chip on flexible(COF) method, a tape automated bonding (TAB) method, or the like may beemployed. The same applies to a method for mounting the IC on the touchsensor unit 70 described later.

A transistor used for the pixel 10 is an OS transistor, which has alower off-state current than a Si transistor.

The OS transistor preferably includes a metal oxide in a channelformation region. The metal oxide used for the OS transistor preferablycontains at least one of indium (In) and zinc (Zn).

Typical examples of such oxide include In-M-Zn oxide, In-M oxide, Zn-Moxide, and In—Zn oxide (the element M is aluminum (Al), gallium (Ga),yttrium (Y), tin (Sn), boron (B), silicon (Si), titanium (Ti), iron(Fe), nickel (Ni), germanium (Ge), zirconium (Zr), molybdenum (Mo),lanthanum (La), cerium (Ce), neodymium (Nd), vanadium (V), beryllium(Be), hafnium (Hf), tantalum (Ta), or tungsten (W), for example).

The off-state current per channel width of 1 μm of an OS transistor canbe low and approximately from 1 yA/μm (y: yocto, 10⁻²⁴) to 1 zA/μm (z:zepto, 10⁻²¹).

It is preferable to use cloud-aligned composite (CAC) OS for the OStransistor. Note that the details of the CAC-OS will be described laterin Embodiment 8.

The transistor used for the pixel 10 is not necessarily an OS transistoras long as its off-state current is low. For example, a transistorincluding a wide-bandgap semiconductor may be used. In some cases, thewide-bandgap semiconductor refers to a semiconductor with a bandgap of2.2 eV or greater. Examples of the wide-bandgap semiconductor includesilicon carbide, gallium nitride, and diamond.

By using the transistor having a low off-state current for the pixel 10,the gate driver 62, the gate driver 63, and the source driver IC 64 canbe temporarily stopped (the temporary stop is referred to as idling stopor IDS driving, as described above) in the case where the display unit60 does not necessarily rewrite an image, that is, a still image isdisplayed.

<Touch Sensor Unit>

The touch sensor unit 70 illustrated in FIG. 1 includes a sensor array71 and a touch sensor IC 72.

The sensor array 71 forms a region where the touch sensor unit 70 canperform detection operation and a user of the display device 50 performsinput on this region with a finger, a stylus, or the like. The sensorarray 71 is provided in a region overlapping with the pixel array 61.The display device 50 displays an image in the display region of thedisplay unit 60 and can obtain information of the position in thedisplay region indicated by the user.

FIG. 2 is a block diagram illustrating a structure example of the touchsensor unit 70. Here, an example in which the touch sensor unit 70 is aprojected capacitive (mutual capacitive) touch sensor unit.

The sensor array 71 includes wirings CL, wirings ML, and a plurality ofcapacitors 404. The capacitors 404 are formed by the wirings CL and MLoverlapping with each other or the wirings CL and ML provided close toeach other.

In FIG. 2, as an example, six wirings CL(1) to CL(6) represent thewirings CL, and six wirings ML(1) to ML(6) represent the wirings ML;however, the number of wirings is not limited to those. The wirings CLare each a wiring to which a pulse voltage is supplied and the wiringsML are each a wiring that detects changes in current.

When proximity or contact of an object (a finger, a stylus, or the like)to the sensor array 71 is detected, the capacitance value of thecapacitor 404 is changed and the touch sensor unit 70 detects a touch.

The sensor array 71 is electrically connected to the touch sensor IC 72through the wirings CL and ML. The touch sensor IC 72 includes a drivercircuit 402 and a detection circuit 403.

The driver circuit 402 is electrically connected to the sensor array 71through the wiring CL. The driver circuit 402 has a function ofoutputting a signal Tx. As the driver circuit 402, a shift registercircuit and a buffer circuit can be used in combination, for example.

The detection circuit 403 is electrically connected to the sensor array71 through the wiring ML. The detection circuit 403 detects a touch onthe touch sensor unit 70 by detecting a signal Rx. The detection circuit403 can include an amplifier circuit and an analog-digital convertercircuit (ADC), for example. The detection circuit 403 has a function ofconverting an analog signal output from the sensor array 71 into adigital signal and outputting the digital signal to the applicationprocessor 80.

Note that a more specific structure example of the touch sensor unit 70is described in Embodiment 2.

<Application Processor>

The application processor 80 is electrically connected to the sourcedriver IC 64 and the touch sensor IC 72.

The application processor 80 has a function of supplying image data tobe displayed on the display unit 60 to the source driver IC 64. Theapplication processor 80 has a function of calculating a differencebetween image data displayed on the display unit 60 at present and imagedata displayed next.

The application processor 80 has a function of transmitting the data ofthe timing when the display unit 60 rewrites an image and the data ofthe timing when the touch sensor unit 70 performs detection operation.The data of the timing when the display unit 60 rewrites an image istransmitted from the application processor 80 to the source driver IC64, and the source driver IC 64 has a function of controlling operationof the gate driver 62 and the gate driver 63. The data of the timingwhen the touch sensor unit 70 performs detection operation istransmitted from the application processor 80 to the touch sensor IC 72.

In the block diagram illustrated in FIG. 1, signals for driving the gatedrivers 62 and 63 are not necessarily supplied through the source driverIC 64. A block diagram in that case is shown in FIG. 18.

In FIG. 18, the application processor 80 supplies signals to sourcedriver ICs 64 a to 64 d, the gate driver 62, and the gate driver 63through a timing controller 810. The timing controller 810 may beincluded in the application processor 80.

The structure illustrated in FIG. 18 includes a plurality of sourcedriver ICs. The number of source driver ICs may be set according to thenumber of pixels of the pixel array 61.

In the structure illustrated in FIG. 18, the number of pixels of thepixel array 61 is preferably larger, for example, 4K (3840×2160) or 8K(7680×4320). A plurality of source driver ICs are provided and a circuitprovided outside the source driver ICs has a function of controlling agate driver, so that the number of terminals of the source driver ICscan be reduced. In the case where the number of the terminals of thesource driver ICs is large, a large amount of force is applied to thesource driver ICs when the source driver ICs are crimped to a substrate,which leads to damage to the source driver ICs. Accordingly, thestructure illustrated in FIG. 18 can prevent the source driver ICs frombeing damaged.

<Pixel Array>

FIG. 3 is a block diagram illustrating a structure example of thedisplay unit 60.

The pixel array 61 includes pixels 10(1,1) to 10(m,n), source linesSL(1) to SL(m), and gate lines GL(1) to GL(n). Here, m and n are each aninteger greater than or equal to 1, i is an integer greater than orequal to 1 and less than or equal to m, and j is an integer greater thanor equal to 1 and less than or equal to n. In FIG. 3, a constantpotential line and the like for forming a power source line or acapacitor are omitted.

The gate drivers 62 and 63 are electrically connected to the pixel array61 through the gate lines GL(1) to GL(n) and the source driver IC 64 iselectrically connected to the pixel array 61 through the source linesSL(1) to SL(m).

A group of pixels 10(i,1) to 10(i,n) arranged in a direction shown by anarrow C1 are electrically connected to a source line SL(i) and a groupof pixels 10(1,j) to 10(m,j) arranged in a direction shown by an arrowR1 are electrically connected to a gate line GL(j).

The gate drivers 62 and 63 drive the gate line GL(j) and select thepixels 10(1,j) to 10(m,j). The source driver IC 64 supplies image datasupplied from the application processor 80 as a data signal to thepixels 10(1,j) to 10(m,j) through the source lines SL(1) to SL(m). Byrepeating this operation from the gate line GL(1) to the gate lineGL(n), the display unit 60 can display an image on the pixel array 61.

Various display elements such as a liquid crystal, electronic paper, anorganic electroluminescence (EL), or a quantum-dot light emitting diode(QLED) can be applied to the pixel 10. Alternatively, for example, ahybrid element in which a liquid crystal element that can be applied asa reflective element and an organic EL element that can be applied as alight-emitting element are combined can be applied to the pixel 10.

Alternatively, for example, a hybrid element in which a liquid crystalelement that can be applied as a reflective element and a transmissiveliquid crystal in which a light source (e.g., LED) and a liquid crystalare combined are combined can be applied to the pixel 10.

<Gate Driver>

FIGS. 4A to 4C are circuit diagrams illustrating a structure example ofthe gate driver that can be applied to the gate driver 62 and the gatedriver 63.

A gate driver illustrated in FIG. 4A includes n shift registers SR andtwo shift registers SR_(DUM) and a start pulse SP, clock signals CLK1 toCLK4, pulse-width control signals PWC1 to PWC4, and a reset signal RESare input to the gate driver from outside. The gate driver illustratedin FIG. 4A includes output terminals OUT_1 to OUT_n+2 and the outputterminals OUT_1 to OUT_n are electrically connected to the gate linesGL(1) to GL(n), respectively.

The shift register SR illustrated in FIG. 4B includes input terminalsCLIN1 to CLIN3, PWIN, LIN, RIN, and RESIN and output terminals SROUT andOUT. As illustrated in FIG. 4A, one of the clock signals CLK1 to CLK4 isinput to each of the input terminals CLIN1 to CLIN3, one of thepulse-width control signals PWC1 to PWC4 is input to the input terminalPWIN, and the reset signal RES is input to the input terminal RESIN.

The output terminals OUT of the shift registers SR are electricallyconnected to the output terminals OUT_1 to OUT_n of the gate driver.When the shift register SR electrically connected to an output terminalOUT_j of the gate driver is called the j-th shift register SR (j is aninteger greater than or equal to 1 and less than or equal to n), theinput terminal LIN of the j-th shift register SR and the input terminalRIN of the j-th shift register SR are electrically connected to theoutput terminal SROUT of the (j−1)-th shift register SR and the outputterminal SROUT of the (j+2)-th shift register SR, respectively. However,the start pulse SP is input to the input terminal LIN of the first shiftregister SR and the input terminal RIN of the (n−1)-th shift register SRand the input terminal RIN of the n-th shift register SR areelectrically connected to the output terminal SROUT of the (n+1)-thshift register SR_(DUM) and the output terminal SROUT of the (n+2)-thshift register SR_(DUM), respectively.

The shift register SR_(DUM) illustrated in FIG. 4C has a structuresimilar to that of the shift register SR except that the input terminalRIN is not provided. Therefore, the description of the shift register SRis referred to for the description of the shift register SR_(DUM).

FIG. 5A is a circuit diagram illustrating a structure example of theshift register SR. In FIG. 5A, a circuit 100 includes transistors 101 to109, a circuit 110 includes transistors 111 to 113, and a circuit 120includes transistors 121 to 123.

Although the transistors 101 to 109, the transistors 111 to 113, and thetransistors 121 to 123, which are OS transistors, are illustrated assingle-gate transistors in FIG. 5A, they may be dual-gate transistorsincluding back gates. Since the transistors 101 to 109, the transistors111 to 113, and the transistors 121 to 123 are OS transistors, theoff-state current of the transistor is reduced, and power consumption ofthe gate driver can be reduced.

Similarly, a circuit diagram illustrating a structure example of theshift register SR_(DUM) is illustrated in FIG. 5B.

FIG. 6 is a timing chart showing waveforms of the start pulse SP, theclock signals CLK1 to CLK4, the pulse-width control signals PWC1 toPWC4, and the output terminals OUT_1 to OUT_n.

In a period P1, pulses are sequentially output from the output terminalsOUT_1 to OUT_n in accordance with the start pulse SP, the clock signalsCLK1 to CLK4, and the pulse-width control signals PWC1 to PWC4.

On the contrary, in a period P2, the pulse-width control signals PWC1 toPWC4 are kept at L level for a certain period. In the example of FIG. 6,pulses are output from the output terminals OUT_1, OUT_2, OUT_n−1, andOUT_n, and pulses are not output from the output terminals OUT_j andOUT_j+1.

In a period Pa and a period Pc, as in the period P1, toggle operation bythe pulse-width control signals PWC1 to PWC4 is performed. In a periodPb, the pulse-width control signals PWC1 to PWC4 are set at L level, sothat the gate driver can output pulses only to the predetermined outputterminals (partial IDS driving described later).

As described above, the gate driver illustrated in FIG. 4A can outputpulses to the output terminals OUT_1 to OUT_n sequentially and canoutput pulses only to the predetermined output terminals by controllingthe pulse-width control signals PWC1 to PWC4.

«Timing Chart»

Next, the relation between image rewriting operation by the display unit60 and detection operation by the touch sensor unit 70 is described. Inthe description of the image rewriting operation by the display unit 60,the operation is divided into the following three modes: the first modein which an image in an entire display region is rewritten (hereinafter,referred to as “normal display”), the second mode in which an image inpart of the display region is rewritten (hereinafter, referred to as“partial IDS driving”), and the third mode in which an image in theentire display region is not rewritten (hereinafter, referred to as “IDSdriving”).

<Normal Display>

Normal display is performed when an image in an entire display regionneeds to be rewritten, for example, when a moving image is displayed inthe entire display region. Here, for easy understanding, the frequencyof image rewriting by the display unit 60 is about 60 times per second(the frame frequency is 60 Hz). In addition, n is 18 in the descriptionof the pixels 10(1,1) to 10(m,n) of the pixel array 61.

When a period in which the display unit 60 rewrites an image is a periodPd, as illustrated in FIG. 7, the gate drivers 62 and 63 drive the gatelines GL(1) to GL(18) and output pulses sequentially. Since imagerewriting is performed in the period Pd, noise such as noise caused bydriving of the gate lines GL(1) to GL(18), noise caused by supply ofdata signals to the source lines SL(1) to SL(m), and noise caused byoperation of the gate drivers 62 and 63 is caused. Therefore, detectionoperation by the touch sensor unit 70 is not preferably performed in theperiod Pd.

In view of this, another period Pt different from the period Pd isprovided and detection operation by the touch sensor unit 70 isperformed in the period Pt. A period Po is a period in which neitherimage rewriting by the display unit 60 nor detection operation by thetouch sensor unit 70 is performed. The period Po is needed for matchingtiming of operation of the display device 50 and operation of a deviceother than the application processor 80 and the display device 50 insome cases; however, the period Po is not necessarily provided unlessneeded.

The display device 50 is designed so that the total time of the periodPd, the period Pt, and the period Po is 1/60 seconds (approximately 16.6ms).

<Partial IDS Driving>

Partial IDS driving is employed when an image in part of a displayregion needs to be rewritten, for example, when a moving image isdisplayed in part of the display region. For example, FIG. 8 is anexample of the application of the display device 50 to a tabletinformation terminal 90.

FIG. 8 is an external view illustrating an embodiment and a usageexample of the tablet information terminal 90. The tablet informationterminal 90 includes a display region 91 that also serves as an inputregion and letters, pictures, and the like can be input thereto with afinger, a stylus, or the like. The display device 50 of one embodimentof the present invention is applied to the display region 91.

FIG. 8 illustrates an example in which a user of the tablet informationterminal 90 learns a letter. The tablet information terminal 90 displaysan illustration 92, a frame 93, and a frame 94. A good example of aletter is displayed within the frame 93. The user writes the same letteras that displayed within the frame 93, in the frame 94 with a stylus 95.The tablet information terminal 90 displays the illustration 92 that isrelated to the letter within the frame 93.

In this case, only an image in the frame 94 needs to be rewritten. Thegate drivers 62 and 63 may drive only the gate lines GL in a regionrelated to the frame 94 (a region A11 shown by a dotted line in FIG. 8).The timing chart shown in FIG. 7 changes into a timing chart shown inFIG. 9, for example.

In FIG. 9, output of pulses to the gate lines GL(1) to GL(9) and thegate lines GL(16) to GL(18) is prevented by controlling the pulse-widthcontrol signals PWC1 to PWC4. The pulses similar to those in normaldisplay are output only to the gate lines GL(10) to GL(15). Such drivingmethod is called partial IDS driving.

In FIG. 9, pulses are not output to the gate lines GL(1) to GL(9); thus,the period Pt in which the touch sensor unit 70 performs detectionoperation can be added. FIG. 10 is an example in which a period Pt2having the same period of time as the period Pt is provided. In thiscase, the touch sensor unit 70 can perform detection operation twice in1/60 seconds (approximately 16.6 ms), so that detection operation can beperformed 120 times per second. Accordingly, input can be smoothlyperformed; thus, the display device 50 is favorable for handwritinginput or the like.

In FIG. 9, pulses are not output to the gate lines GL(16) to GL(18) aswell as the gate lines GL(1) to GL(9), so that the period Pt2 can beseparately provided.

Since image rewriting is unnecessary in the period Pt2, noise caused bydriving of the gate lines GL(1) to GL(18) and noise caused by supply ofdata signals to the source lines SL(1) to SL(m) are not caused.Therefore, detection operation by the touch sensor unit 70 is preferablyperformed in the period Pt2.

Also in the period Pt2, the clock signals CLK1 to CLK4 are supplied tothe gate drivers 62 and 63; thus, in the case where higher detectionsensitivity is needed, each of the shift register SR and the shiftregister SR_(DUM) of each of the gate driver 62 and the gate driver 63can be a decoder circuit not using a clock signal.

<IDS Driving>

IDS driving is employed when an image in an entire display region doesnot need to be rewritten, for example, when a still image is displayedin an entire display region. In that case, the period Pd in which thedisplay unit 60 rewrites an image becomes unnecessary in the timingchart shown in FIG. 7; therefore, a timing chart is shown as in FIG. 11.

In FIG. 11, the gate drivers 62 and 63 are stopped and pulses are notoutput to the gate lines GL(1) to GL(18). In this case, the period Ptand the period Pt2 can be freely provided in a period of 1/60 seconds(approximately 16.6 ms) other than the period Po; therefore, input canbe smoothly performed. If necessary, a period in which the touch sensorunit 70 performs detection operation can be further added.

In the IDS driving, an image does not need to be rewritten as long as astill image is displayed; however, in practice, a time during which thepixel 10 using a transistor having a low off-state current can hold acharge, inversion driving occurring when a display element of the pixel10 is a liquid crystal element, or the like needs to be taken intoconsideration.

Furthermore, the IDS driving and the partial IDS driving are favorablefor a portable information terminal because power consumption of adisplay unit can be reduced.

«Flow chart»

Then, a state in which three operation modes (normal display, partialIDS driving, and IDS driving) are switched after an electronic device towhich the display device 50 is applied is turned on is described using aflow chart in FIG. 12.

When the electronic device to which the display device 50 is applied isturned on (Step S1), first, normal display with a frame frequency of 60Hz is performed (Step S2). After a while, startup operation isterminated and it is determined whether image rewriting in an entiredisplay region is unnecessary or not (Step S3). The determination can bemade by calculating a difference between image data displayed at presentand image data displayed next by the application processor 80.

When image rewriting in the entire display region is unnecessary, theIDS driving is performed (Step S4). When image rewriting in the entiredisplay region is not unnecessary, it is determined whether imagerewriting in part of the display region is unnecessary or not (Step S5).The determination whether image rewriting in part of the display regionis unnecessary or not is made by the application processor 80 as in theStep S3. When image rewriting in part of the display region isunnecessary, the partial IDS driving is performed (Step S6). When atouch is detected in the IDS driving or the partial IDS driving (StepS7), it is determined again whether image rewriting in the entiredisplay region is unnecessary or not (Step S3).

When it is determined in Step S3 that image rewriting in the entiredisplay region is not unnecessary and it is determined in Step S5 thatimage rewriting in part of the display region is not unnecessary, normaldisplay is performed (Step S2).

Next, operation that still text (letters) is displayed on an informationterminal that is an electronic device to which the display device 50 isapplied, and a user marks a part on which the user focuses is describedusing FIGS. 13A to 13D and FIG. 14.

FIGS. 13A to 13D illustrate a usage example of the information terminalto which the display device 50 is applied and the states of signalsinput to the gate drivers 62 and 63. The signals are the clock signalCLK, which is one of the clock signals CLK1 to CLK4, and the pulse-widthcontrol signals PWC1 and PWC2. FIG. 14 is a flow chart showing operationof the information terminal illustrated in FIGS. 13A to 13D.

FIG. 13A illustrates a state immediately after an application is startedup (Step S11 in FIG. 14). Normal display is performed and the clocksignal CLK and the pulse-width control signals PWC1 and PWC2 performtoggle operation.

In FIG. 13B, still text is displayed; thus, the IDS driving is performed(Step S12 in FIG. 14). In the IDS driving, the clock signal CLK and thepulse-width control signals PWC1 and PWC2 are kept at L level and thegate drivers 62 and 63 are stopped.

In FIG. 13C, a touch by a stylus is detected (Step S13 in FIG. 14). Thepartial IDS driving is performed (Step S14 in FIG. 14) and the clocksignal CLK performs toggle operation (FIG. 13D). The start pulse SP isalso input to the gate drivers 62 and 63 so that the gate drivers 62 and63 start operation; however, the pulse-width control signals PWC1 andPWC2 are at L level for a while (Steps S16 and S17 in FIG. 14). When theinput start pulse SP shifts the shift register and is transferred to Klines before a region where an image needs to be rewritten, the touchsensor unit 70 stops operation (Steps S17 and S18 in FIG. 14). Althoughit depends on the circuit configuration, K is an integer at least 1 ormore.

When the start pulse SP is transferred to the region where imagerewriting is needed, the pulse-width control signals PWC1 and PWC2 alsoperform toggle operation and the gate drivers 62 and 63 output pulses tothe gate line GL. Then, image data is written to the pixel 10 as a datasignal (Steps S19 and S20 in FIG. 14).

After image rewriting in the region where image rewriting is needed isterminated, the pulse-width control signals PWC1 and PWC2 become L leveland the touch sensor unit 70 resumes operation. When the start pulse SPis transferred to the last stage of the shift register, the shiftregister is reset by an RES signal (Steps S21, S22, and S23 in FIG. 14).

When next touch is detected (Step S15 in FIG. 14), the operation of StepS14 and the operation after Step S15 in FIG. 14 are repeated. When nexttouch is not detected, the IDS driving is performed again (Step S12 inFIG. 14).

As described above, in the electronic device to which the display device50 is applied, three operation modes (normal display, partial IDSdriving, and IDS driving) can be switched appropriately. The displaydevice 50 performs accurate detection operation by the touch sensor unit70 at the timing when an effect of noise is small, and the displaydevice 50 enables smooth input when the partial IDS driving or the IDSdriving is performed. Furthermore, when the partial IDS driving or theIDS driving is performed, power consumption of image rewriting operationcan be reduced.

In the usage example of FIGS. 13A to 13D, a display example of thedisplay device 50 is an example in which a transmissive or reflectiveliquid crystal element is applied to the pixel 10, for example.

Alternatively, in the usage example of FIGS. 13A to 13D, a hybridelement in which a reflective element and a light-emitting element arecombined may be applied to the pixel 10. In this case, still text and amark may be displayed using the reflective element and thelight-emitting element, respectively. The reflective element displayingthe still text can perform the IDS driving.

An operation similar to that can be performed when a light-emittingelement such as an organic EL is applied to the pixel 10 andabove-described accurate detection, smooth input, and reduction in powerconsumption of image rewriting operation can be achieved. In this case,the light-emitting area of the light-emitting element influences powerconsumption of light emission. Therefore, in the structure of the usageexample of FIGS. 13A to 13D, it is preferable that a background is black(light is not emitted) and only a necessary portion emits light asillustrated in FIGS. 15A to 15D.

This embodiment can be implemented in combination with any otherembodiment as appropriate.

(Embodiment 2)

In this embodiment, a structure example of the touch sensor unit 70mentioned in the above embodiment is described with reference to FIGS.16A to 16C and FIGS. 17A and 17B.

A specific structure example of the touch sensor unit 70 is describedwith reference to FIGS. 16A to 16C and FIGS. 17A and 17B.

FIG. 16A is a top view of the touch sensor unit 70. FIGS. 16B and 16Care each a projection view illustrating part of FIG. 16A.

FIG. 17A is a top view of a portion in which a control line and asensing signal line are adjacent to each other. FIG. 17B is a projectionview that schematically illustrates an electric field generated in theadjoining portion.

The touch sensor unit 70 includes the sensor array 71. The sensor array71 includes a wiring CL(g), a wiring ML(h), and a conductive film (seeFIG. 16A). Note that g and h are each an integer of 2 or more.

For example, a conductive film divided into a plurality of regions canbe used for the sensor array 71 (see FIG. 16A). This enables the samepotential or different potentials to be supplied to the plurality ofregions.

Specifically, a conductive film divided into a conductive film that canbe used as the wiring CL(g) and a conductive film that can be used asthe wiring ML(h) can be used for the sensor array 71. The conductivefilms obtained by dividing a conductive film into a plurality of regionscan each have a comb-like shape, for example (see an electrode CE(1), anelectrode ME(1), and an electrode ME(2) in FIGS. 17A and 17B). In thismanner, the divided conductive films can be used as electrodes ofsensing elements.

For example, a conductive film that can be used as the wiring CL(1), aconductive film that can be used as the wiring ML(1), and a conductivefilm that can be used as the wiring ML(2), which are obtained bydividing a conductive film, are adjacent to each other in an adjoiningportion X0 (see FIG. 16A, FIG. 16C or FIGS. 17A and 17B).

A sensing element 475(g,h) is electrically connected to the wiring CL(g)and the wiring ML(h) (see FIG. 16A).

The wiring CL(g) has a function of supplying the signal Tx, and thewiring ML(h) has a function of receiving the signal Rx.

The wiring ML(h) includes a conductive film BR(g,h) (see FIG. 16B). Theconductive film BR(g,h) includes a region overlapping with the wiringCL(g).

Note that the sensing element 475(g,h) includes an insulating film. Theinsulating film includes a region positioned between the wiring ML(h)and the conductive film BR(g,h). Thus, a short circuit between thewiring ML(h) and the conductive film BR(g,h) can be prevented.

The electrode CE(1) is electrically connected to the wiring CL(1), andthe electrode ME(1) is electrically connected to the wiring ML(1) (seeFIGS. 17A and 17B).

In a similar manner, an electrode CE(g) is electrically connected to thewiring CL(g), and an electrode ME(h) is electrically connected to thewiring ML(h).

A sensing element 475(1,1) detects a touch by detecting a change in thevalue of the capacitance formed between the electrode CE(1) and theelectrode ME(1) (see FIGS. 17A and 17B).

In a similar manner, the sensing element 475(g,h) detects a touch bydetecting a change in the value of the capacitance formed between theelectrode CE(g) and the electrode ME(h).

Conductive films which can be formed in the same process can be used asthe wiring CL(1) and the electrode CE(1). Conductive films which can beformed in the same process can be used as the wiring ML(1) and theelectrode ME(1) (see FIGS. 17A and 17B).

In a similar manner, conductive films which can be formed in the sameprocess can be used as the wiring CL(g) and the electrode CE(g).Conductive films which can be formed in the same process can be used asthe wiring ML(h) and the electrode ME(h).

For example, a light-transmitting conductive film can be used as each ofthe electrodes CE(g) and ME(h). Alternatively, a conductive film havingan opening or a comb-like shape in a region overlapping with the pixelcan be used as each of the electrodes CE(g) and ME(h). Accordingly, anobject that approaches the region overlapping with the display panel canbe sensed without disturbing display on the display panel.

Note that this embodiment can be combined with any of the otherembodiments in this specification as appropriate.

(Embodiment 3)

In this embodiment, a circuit configuration example of the pixel 10described in the above embodiment is described with reference to FIG.19, FIG. 20, and FIGS. 21A and 21B.

<Pixel 10 a>

FIG. 19 illustrates an example of a pixel circuit that can be used for apanel including a liquid crystal element. A pixel 10 a illustrated inFIG. 19 includes a transistor 301, a capacitor 303, and a liquid crystalelement 304 functioning as a display element.

A gate (first gate) of the transistor 301 is electrically connected tothe gate line GL, a back gate (second gate) of the transistor 301 iselectrically connected to the gate, a first terminal of the transistor301 is electrically connected to the source line SL, and a secondterminal of the transistor 301 is electrically connected to a firstterminal of the capacitor 303 and a first terminal of the liquid crystalelement 304. A node of the second terminal of the transistor 301, thefirst terminal of the capacitor 303, and the first terminal of theliquid crystal element 304 is referred to as a node 302. The transistor301 has a function of controlling whether to write a data signal to thenode 302.

A second terminal of the capacitor 303 is electrically connected to awiring (also referred to as a capacitor line CL) to which a particularpotential is supplied. The value of the potential of the capacitor lineCL is set in accordance with the specifications of the pixel 10 a asappropriate. The capacitor 303 has a function as a storage capacitor forstoring data written to the node 302.

The potential of a second terminal of the liquid crystal element 304 isset in accordance with the specifications of the pixel 10 a asappropriate. The alignment state of a liquid crystal in the liquidcrystal element 304 depends on data written to the node 302. A commonpotential may be supplied to the second terminal of the liquid crystalelement 304 included in each of the pixels 10 a.

A liquid crystal element that can be driven by any of the followingdriving methods can be used as the liquid crystal element 304: an IPSmode, a TN mode, an FFS mode, an ASM mode, an OCB mode, a ferroelectricliquid crystal (FLC) mode, an antiferroelectric liquid crystal (AFLC)mode, a VA mode, an MVA mode, a patterned vertical alignment (PVA) mode,an electrically controlled birefringence (ECB) mode, a continuouspinwheel alignment (CPA) mode, and an advanced super-view (ASV) mode.

For example, a liquid crystal material having a resistivity of greaterthan or equal to 1.0×10¹³ Ω·cm, preferably greater than or equal to1.0×10¹⁴ Ω·cm, more preferably greater than or equal to 1.0×10¹⁵ Ω·cm,is used for the liquid crystal element 304. This can suppress avariation in the transmittance of the liquid crystal element 304.Alternatively, flickering of the liquid crystal element 304 can besuppressed. Alternatively, the rewriting frequency of the liquid crystalelement 304 can be reduced.

For example, a liquid crystal material containing a nematic liquidcrystal, a thermotropic liquid crystal, a low-molecular liquid crystal,a high-molecular liquid crystal, a polymer dispersed liquid crystal, orthe like can be used for the liquid crystal element 304. Alternatively,a liquid crystal material which exhibits a cholesteric phase or the likecan be used. Alternatively, a liquid crystal material which exhibits ablue phase can be used.

Alternatively, for example, a liquid crystal material containing adichroic dye can be used for the liquid crystal element 304. Note that aliquid crystal material containing a dichroic dye is called a guest-hostliquid crystal.

Specifically, a material that has high absorbance in the major axisdirection of molecules and a material that has low absorbance in theminor-axis direction orthogonal to the major axis direction can be usedfor the dichroic dye. It is preferable to use a material with a dichroicratio of 10 or higher, further preferably 20 or higher for the dichroicdye.

An azo dye, an anthraquinone dye, a dioxazine dye, or the like can beused as a dichroic dye, for example.

Two liquid crystal layers including a dichroic dye having homogeneousalignment that are stacked to be orthogonally aligned with each othercan be used as a layer containing a liquid crystal material. With thestructure, light can be easily absorbed in all directions and contrastcan be increased.

A phase transition guest-host liquid crystal or a liquid crystal inwhich a droplet containing a guest-host liquid crystal dispersed in apolymer may be used for the liquid crystal element 304.

Next, an operation example of the pixel 10 a is described.

First, the pixels 10 a are sequentially selected row by row by the gatedrivers 62 and 63, whereby the transistors 301 are turned on and data iswritten to the node 302.

Then, the transistor 301 is turned off and the data written to the node302 is held. The amount of light transmitted through the liquid crystalelement 304 is determined in accordance with the data written to thenode 302. This operation is sequentially performed row by row; thus, animage is displayed on the display region.

When the transistor 301 includes a back gate, the current drivingcapability of the transistor 301 can be increased. Note that the backgate is not necessarily provided in the transistor 301 according tocircumstances. The transistor 301 not including the back gate can befabricated by a simplified process.

A transistor including a metal oxide in a channel formation region (OStransistor) is preferably used as the transistor 301. In the case wherean OS transistor is used as the transistor 301, the pixel 10 a can holddata written to the node 302 for a long time; thus, the frequency ofrefreshing image data can be reduced while a still image is displayed.That is, the pixel 10 a can perform the IDS driving. Consequently, powerconsumption of the display device 50 can be low.

<Pixel 10 b>

FIG. 20 illustrates an example of a pixel 10 b that can be used for apanel including a light-emitting element.

The pixel 10 b is electrically connected to the gate line GL, the sourceline SL, a wiring CTL, and a wiring ANL. The pixel 10 b includes atransistor 311, a transistor 312, a capacitor 310, and a light-emittingelement 314.

The light-emitting element 314 includes a pair of terminals (an anodeand a cathode). As the light-emitting element 314, an element which cancontrol the luminance with current or voltage can be used. As thelight-emitting element 314, for example, a light-emitting elementutilizing electroluminescence (also referred to as an EL element) can beused. An EL element includes a light-emitting layer (also referred to asan EL layer) between a pair of electrodes.

Although the transistors 311 and 312 are n-channel transistors in FIG.20, one or both of the transistors 311 and 312 may be p-channeltransistors. The transistors 311 and 312 each include a back gate(second gate) electrically connected to a gate (first gate). With such adevice structure, the current drive capability of the transistors 311and 312 can be improved.

The transistor 311 is a pass transistor which connects the gate of thetransistor 312 (a node 315) and the source line SL. The transistor 312is a driving transistor and functions as a current source of currentsupplied to the light-emitting element 314. In accordance with theamount of drain current of the transistor 312, the luminance of thelight-emitting element 314 is adjusted. The capacitor 310 is a storagecapacitor which stores voltage between the node 315 and the wiring ANL.

The pixels 10 b are sequentially selected row by row by the gate drivers62 and 63, whereby the transistors 311 are turned on and data is writtento the node 315.

Then, the transistor 311 is turned off and the data written to the node315 is held. The luminance of the light-emitting element 314 isdetermined in accordance with the data written to the node 315. Thisoperation is sequentially performed row by row; thus, an image isdisplayed on the display region.

An OS transistor is preferably used as the transistor 311. In the casewhere an OS transistor is used as the transistor 311, the pixel 10 b canhold data written to the node 315 for a long time; thus, the frequencyof refreshing image data can be reduced while a still image isdisplayed. That is, the pixel 10 b can perform the IDS driving.Consequently, power consumption of the display device 50 can be low.

<Pixel 10 c>

FIG. 21A illustrates an example of a pixel 10 c that can be used for apanel including a light-emitting element.

In the pixel 10 c, the wiring ML and a transistor 313 are added to thepixel 10 b illustrated in FIG. 20. The transistor 313 is a passtransistor which connects the wiring ML and the anode of thelight-emitting element 314.

Variation in the drive capability of the transistor 312 causes variationin the luminance of the light-emitting element 314, which results indecrease in display quality. The pixel 10 c has a function of correctingvariation in the luminance of the light-emitting element 314 bymonitoring a drain current of the transistor 312.

FIG. 21B shows an example of a timing chart of the potential of the gateline GL illustrated in FIG. 21A and an image signal supplied to thesource line SL. Note that in the timing chart in FIG. 21B, all thetransistors included in the pixel 10 c are n-channel transistors.

A period T1 is a writing operation period and the light-emitting element314 does not emit light during the period. A high-level potential issupplied to the gate line GL, and the transistors 311 and 313 are turnedon. A potential V_(data) is supplied to the source line SL as an imagesignal. The potential V_(data) is supplied to the gate of the transistor312 through the transistor 815 311.

It is preferable that, in the period T1, the potential of the wiring MLbe lower than the sum of the potential of the wiring CTL and thethreshold voltage V_(the) of the light-emitting element 314, and thatthe potential of the wiring ANL be higher than the potential of thewiring ML. With the above configuration, the drain current of thetransistor 312 can be made to flow preferentially through the wiring MLinstead of the light-emitting element 314.

A period T2 is a light emission period and the light-emitting element314 emits light during the period. A low-level potential is supplied tothe gate line GL, and the transistors 311 and 313 are turned off. Sincethe transistor 311 is turned off, the potential V_(data) is held at thegate of the transistor 312. A potential V_(ano) is supplied to thewiring ANL, and a potential V_(cat) is supplied to the wiring CTL. Thepotential V_(ano) is preferably higher than the sum of the potentialV_(cat) and the threshold voltage V_(the) of the light-emitting element314. The potential difference between the wiring ANL and the wiring CTLallows the drain current of the transistor 312 to flow into thelight-emitting element 314; thus, the light-emitting element 314 emitslight.

A period T3 is a monitor period in which the drain current of thetransistor 312 is obtained. A high-level potential is supplied to thegate line GL, and the transistors 311 and 313 are turned on. A potentialthat the gate voltage of the transistor 312 is higher than the thresholdvoltage V_(th) thereof is applied to the source line SL. It ispreferable that the potential of the wiring ML be lower than the sum ofthe potential of the wiring CTL and the threshold voltage V_(the) of thelight-emitting element 314, and that the potential of the wiring ANL behigher than the potential of the wiring ML. With the aboveconfiguration, the drain current of the transistor 312 can be made toflow preferentially through the wiring ML instead of the light-emittingelement 314.

A current I_(MON) output from the pixel 10 c to the wiring ML in theperiod T3 corresponds to the drain current flowing into the transistor312 during the light emission period. The current I_(MON) is supplied toa monitor circuit. The monitor circuit analyzes the current I_(MON) andgenerates a correction signal on the basis of the analysis result.Through the operation, deviation of the luminance of the pixels 10 c canbe corrected.

The monitor operation is not necessarily performed after thelight-emitting operation. For example, in the pixel 10 c, the monitoroperation can be performed after the cycle of data writing operation andlight-emitting operation is repeated plural times. Alternatively, afterthe monitor operation, the light-emitting element 314 may be broughtinto a non-light-emitting state by writing a data signal correspondingto the lowest grayscale level [0] to the pixel 10 c.

As in the pixel 10 b, an OS transistor is preferably used as thetransistor 311 in the pixel 10 c. In the case where an OS transistor isused as the transistor 311, the pixel 10 c can perform the IDS driving.Consequently, power consumption of the display device 50 can be low.

The back gate is not necessarily provided in each of the transistors311, 312, and 313 illustrated in FIG. 20 and FIG. 21A according tocircumstances. The transistors 311, 312, and 313 not including the backgates can be fabricated by a simplified process.

Note that this embodiment can be combined with any of the otherembodiments in this specification as appropriate.

(Embodiment 4)

In this embodiment, structure examples of the display device 50described in the above embodiment is described with reference to FIGS.22A to 22D, FIGS. 23A and 23B, FIGS. 24A and 24B, FIGS. 25A and 25B,FIGS. 26A to 26C, FIG. 27, and FIG. 28.

FIGS. 22A to 22D, FIGS. 23A and 23B, and FIGS. 24A and 24B are schematiccross-sectional views each illustrating the display device 50. Note thatin the schematic cross-sectional views in FIGS. 22A to 22D, FIGS. 23Aand 23B, and FIGS. 24A and 24B, only components necessary for describingthe operation of a touch sensor are illustrated. For example, an elementsuch as a transistor is provided over a substrate 411 in some cases butis not illustrated in these drawings.

<FIGS. 22A to 22D>

The display device 50 illustrated in FIG. 22A includes the substrate411, a substrate 412, an FPC 413, a wiring 414, a liquid crystal element420, a coloring film 431, an electrode 441, and the like.

The liquid crystal element 420 includes an electrode 421, an electrode422, and a liquid crystal 423. The electrode 422 is positioned over theelectrode 421 with an insulating film 424 provided therebetween. Theelectrode 421 functions as a common electrode of the liquid crystalelement 420, and the electrode 422 functions as a pixel electrode.

The electrode 421 and the electrode 422 are provided so as to form anelectric field that intersects the thickness direction of the liquidcrystal 423 (the A1-A2 direction in the drawing). As the liquid crystal423, a liquid crystal material that operates in an in-plane-switching(IPS) mode, a fringe field switching (FFS) mode, or a vertical alignmentin-plane-switching (VA-IPS) mode can be used.

A touch sensor can perform detection by utilizing the capacitance formedbetween the electrode 441 provided on the substrate 412 side and theelectrode 421 functioning as one of a pair of electrodes of the liquidcrystal element 420.

The electrode 441 is formed over a surface of the substrate 412 on thedisplay surface side (the side opposite to the substrate 411). Theelectrode 441 is electrically connected to an FPC 443 provided on thesubstrate 412 side. The electrode 421 is electrically connected to theFPC 413 provided on the substrate 411 side via the wiring 414.

In the display device 50 illustrated in FIG. 22A, the electrode 421 andthe electrode 422 may function as a pixel electrode and a commonelectrode, respectively, and a touch may be detected by utilizing thecapacitance formed between the electrode 441 and the electrode 422. FIG.22B is a schematic view illustrating the case.

In the display device 50 illustrated in FIG. 22A, the electrode 441 maybe provided between the substrate 412 and the liquid crystal 423. FIG.22C is a schematic view illustrating the case.

In the display device 50 illustrated in FIG. 22B, the electrode 441 maybe provided between the substrate 412 and the liquid crystal 423. FIG.22D is a schematic view illustrating the case.

In the structures illustrated in FIGS. 22A to 22D, the one electrode ofthe liquid crystal element 420 can also serve as one of a pair ofelectrodes of the touch sensor. Consequently, the manufacturing processcan be simplified and the manufacturing costs can be reduced.

<FIGS. 23A and 23B>

In the display device 50 illustrated in FIG. 22A, the electrode 441 andthe FPC 443 are not necessarily provided. FIG. 23A is a schematic viewillustrating the case.

In FIG. 23A, electrodes 421 a and 421 b functioning as the commonelectrodes of the liquid crystal element 420 also function as the pairof electrodes of the touch sensor.

In the display device 50 illustrated in FIG. 23A, the electrode 422 maybe used as a common electrode. FIG. 23B is a schematic cross-sectionalview illustrating the case. In FIG. 23B, an electrode 422 a and anelectrode 422 b function as the pair of electrodes of the touch sensor.

In the structure illustrated in FIG. 23A or FIG. 23B, the one electrodeof the liquid crystal element 420 can serve as both of the pair ofelectrodes of the touch sensor. Thus, the manufacturing process can besimplified as compared with the cases illustrated in FIGS. 22A and 22B.

<FIGS. 24A and 24B>

In the display device 50 illustrated in FIG. 22A, the pair of electrodesof the touch sensor may be formed of only the electrode 441. FIG. 24A isa schematic cross-sectional view illustrating the case.

In FIG. 24A, an electrode 441 a and an electrode 441 b over thesubstrate 412 function as the pair of electrodes of the touch sensor.

In the display device 50 illustrated in FIG. 24A, the electrode 441 aand the electrode 441 b may be provided between the substrate 412 andthe liquid crystal 423. FIG. 24B is a schematic cross-sectional viewillustrating the case.

In FIG. 24A or FIG. 24B, the electrode 441 a and the electrode 441 b arespaced apart from the electrodes of the liquid crystal element 420 (theelectrode 421 and the electrode 422). Therefore, an electric fieldformed by the electrode 441 a and the electrode 441 b does not interferewith an electric field formed by the liquid crystal element 420.Furthermore, the electrode 441 a and the electrode 441 b are spacedapart from a wiring, a transistor, and the like which are formed overthe substrate 411 and might serve as noise generation sources.Therefore, the display device 50 illustrated in FIG. 24A or FIG. 24B canhave a high touch sensitivity.

<FIGS. 25A and 25B>

In the case where the electrodes of the touch sensor are arranged as inFIG. 24A or FIG. 24B, a liquid crystal that enables display byapplication of an electric field perpendicular to the substrate 411 canbe used as the liquid crystal 423. FIGS. 25A and 25B are schematiccross-sectional views illustrating the case.

In FIGS. 25A and 25B, the electrode 421 and the electrode 422 arevertically stacked with the liquid crystal 423 positioned therebetween.Also in this case, an electric field formed by the electrode 441 a andthe electrode 441 b does not interfere with an electric field formed bythe liquid crystal element 420. The liquid crystal 423 can employ atwisted nematic (TN) mode, a vertical alignment (VA) mode, amulti-domain vertical alignment (MVA) mode, an optically compensatedbirefringence (OCB) mode, or the like.

<FIGS. 26A to 26C>

In the case where the electrodes of the touch sensor are provided as inFIG. 24A or FIG. 24B, an EL element can be used as the display element.FIGS. 26A to 26C are schematic cross-sectional views illustrating thecase.

In the display device 50 illustrated in FIG. 26A, the liquid crystalelement 420 illustrated in FIG. 24A is replaced with an EL element 463.Similarly, in the display device 50 illustrated in FIG. 26B, the liquidcrystal element 420 illustrated in FIG. 24B is replaced with the ELelement 463.

In FIGS. 26A and 26B, the EL element 463 includes an electrode 464, anEL layer 465, and an electrode 466. The electrode 464 functions as oneof an anode and a cathode of the EL element 463, and the electrode 466functions as the other of the anode and the cathode of the EL element463. The electrode 466 functions as a reflective film, and the electrode464 has a function of transmitting visible light. The EL layer 465includes a light-emitting layer, and, when voltage is applied betweenthe electrode 464 and the electrode 466, current flows through the ELlayer 465, so that the EL layer 465 emits light. The light emitted fromthe EL layer 465 is extracted to the outside through the coloring film431 and the substrate 412.

In each of the display devices 50 illustrated in FIGS. 26A and 26B, theelectrodes 441 a and 441 b may be provided on the substrate 411. FIG.26C is a schematic cross-sectional view illustrating the case. In thiscase, the electrode 464 functions as a reflective film, and theelectrode 466 has a function of transmitting visible light. The lightemitted from the EL layer 465 is extracted to the outside through thecoloring film 431 and the substrate 411. In FIG. 26C, the electrode 441a and the electrode 441 b may be provided between the substrate 411 andthe EL element 463.

In FIGS. 26A to 26C, an electric field formed by the electrode 441 a andthe electrode 441 b is not blocked by the EL element 463. Thus, thetouch sensor can have a high touch sensitivity.

More specific examples of the structure of the display device 50 aredescribed with reference to FIG. 27 and FIG. 28.

<FIG. 27>

FIG. 27 is a cross-sectional view showing details of the schematiccross-sectional view of the display device 50 illustrated in FIG. 23A.

The display device illustrated in FIG. 27 includes an electrode 625, andthe electrode 625 is electrically connected to a terminal of the FPC 413via an anisotropic conductive layer 626. The electrode 625 iselectrically connected to the wiring 414 in an opening formed in aninsulating layer 624. The electrode 625 is formed of the same conductivelayer as a first electrode 422.

The pixel 10 and the gate driver 62 provided over the first substrate411 include a plurality of transistors. In FIG. 27, a transistor 601included in the pixel 10 and a transistor 602 included in the gatedriver 62 are illustrated as an example. In FIG. 27, the insulatinglayer 624 is provided over the transistor 601 and the transistor 602.

«Transistors 601 and 602»

In the transistor 601 and the transistor 602, an electrode 616 isprovided over the substrate 411, an insulating layer 621 is providedover the electrode 616, a semiconductor layer 612 is provided over theinsulating layer 621, an insulating layer 622 is provided over thesemiconductor layer 612, and an electrode 617 is provided over theinsulating layer 622. An electrode 610 and an electrode 611 are incontact with the semiconductor layer 612. The electrode 610 and theelectrode 611 are formed of the same conductive layer as the wiring 414.

In each of the transistors 601 and 602, the electrode 617 functions as afirst gate electrode (top gate), the electrode 616 functions as a secondgate electrode (back gate), the electrode 610 functions as one of asource electrode and a drain electrode, and the electrode 611 functionsas the other of the source electrode and the drain electrode.

In the case where the transistor 601 and the transistor 602 each includethe top gate and the back gate, the on-state current of the transistorscan be increased. Moreover, the threshold voltage of the transistors canbe controlled.

In each of the transistor 601 and the transistor 602, the semiconductorlayer 612 functions as a channel formation region. The semiconductorlayer 612 may be formed using a metal oxide, for example.

When a metal oxide is used for each of the semiconductor layer 612, themetal oxide preferably includes at least one of indium (In) and zinc(Zn). Typical examples of such oxide include In oxide, Zn oxide, In—Znoxide, In-M-Zn oxide, In-M oxide, and Zn-M oxide (the element M isaluminum (Al), gallium (Ga), yttrium (Y), tin (Sn), boron (B), silicon(Si), titanium (Ti), iron (Fe), nickel (Ni), germanium (Ge), zirconium(Zr), molybdenum (Mo), lanthanum (La), cerium (Ce), neodymium (Nd),vanadium (V), beryllium (Be), hafnium (Hf), tantalum (Ta), or tungsten(W), for example).

In the case where OS transistors are used as the transistors 601 and602, the current in an off state (the off-state current) can bedecreased. Accordingly, an electrical signal such as an image signal canbe held for a longer period, and a writing interval can be set longer inan on state. Accordingly, the frequency of refresh operation can bereduced, which leads to an effect of suppressing power consumption.

«Liquid Crystal Element 420»

An example of a liquid crystal display panel using a liquid crystalelement as a display element is illustrated in FIG. 27. In FIG. 27, theliquid crystal element 420 as a display element includes the firstelectrode 422, the second electrode 421, and the liquid crystal 423.Note that an alignment film 631 and an alignment film 632 are providedso that the liquid crystal 423 is interposed therebetween. The secondelectrode 421 is provided such that an electric field in the directionintersecting the thickness direction of the layer containing a liquidcrystal material is formed between the second electrode 421 and thefirst electrode 422.

For example, a liquid crystal material that operates in an FFS mode, aVA-IPS mode, or an IPS mode can be used as the liquid crystal 423.

«Substrate 411»

For the substrate 411 or the like, an organic material, an inorganicmaterial, a composite material of an organic material and an inorganicmaterial, or the like can be used. For example, an inorganic material,such as glass, ceramic, or a metal, can be used for the substrate 411 orthe like.

Specifically, non-alkali glass, soda-lime glass, potash glass, crystalglass, aluminosilicate glass, tempered glass, chemically tempered glass,quartz, sapphire, or the like can be used for the substrate 411 or thelike. Specifically, an inorganic oxide film, an inorganic nitride film,an inorganic oxynitride film, or the like can be used for the substrate411 or the like.

For example, a silicon oxide film, a silicon nitride film, a siliconoxynitride film, an aluminum oxide film, or the like can be used for thesubstrate 411 or the like. Stainless steel, aluminum, or the like can beused for the substrate 411 or the like.

For example, a single crystal semiconductor substrate or apolycrystalline semiconductor substrate of silicon or silicon carbide, acompound semiconductor substrate of silicon germanium or the like, or anSOI substrate can be used for the substrate 411 or the like. Thus, asemiconductor element can be provided over the substrate 411 or thelike.

For example, an organic material such as a resin, a resin film, orplastic can be used for the substrate 411 or the like. Specifically, aresin film or a resin plate of polyester, polyolefin, polyamide,polyimide, polycarbonate, an acrylic resin, or the like can be used forthe substrate 411 or the like.

For example, a composite material formed by attaching a metal plate, athin glass plate, or a film of an inorganic material to a resin film orthe like can be used for the substrate 411 or the like. For example, acomposite material formed by dispersing a fibrous or particulate metal,glass, inorganic material, or the like into a resin film can be used forthe substrate 411 or the like. For example, a composite material formedby dispersing a fibrous or particulate resin, organic material, or thelike into an inorganic material can be used for the substrate 411 or thelike.

A single-layer material or a material obtained by stacking a pluralityof layers can be used for the substrate 411 or the like. For example, alayered material in which a base, an insulating film that preventsdiffusion of impurities contained in the base, and the like are stackedcan be used for the substrate 411 or the like. Specifically, a materialobtained by stacking glass and one or a plurality of films that areselected from a silicon oxide layer, a silicon nitride layer, a siliconoxynitride layer, and the like and that prevent diffusion of impuritiescontained in the glass can be used for the substrate 411 or the like.Alternatively, a material obtained by stacking a resin and a film thatprevents diffusion of impurities that penetrate the resin, such as asilicon oxide film, a silicon nitride film, or a silicon oxynitridefilm, can be used for the substrate 411 or the like.

Specifically, a resin film, a resin plate, a layered material, or thelike of polyester, polyolefin, polyamide, polyimide, polycarbonate, anacrylic resin, or the like can be used for the substrate 411 or thelike.

Specifically, a material including polyester, polyolefin, polyamide(e.g., nylon or aramid), polyimide, polycarbonate, polyurethane, anacrylic resin, an epoxy resin, or a resin having a siloxane bond, suchas silicone, can be used for the substrate 411 or the like.

Specifically, polyethylene terephthalate (PET), polyethylene naphthalate(PEN), polyethersulfone (PES), an acrylic resin, or the like can be usedfor the substrate 411 or the like. Alternatively, a cycloolefin polymer(COP), a cycloolefin copolymer (COC), or the like can be used.

Alternatively, paper, wood, or the like can be used for the substrate411 or the like.

For example, a flexible substrate can be used for the substrate 411 orthe like.

Note that a transistor, a capacitor, or the like can be directly formedon the substrate. Alternatively, a transistor, a capacitor, or the likecan be formed over a substrate which is for use in the manufacturingprocess and can withstand heat applied in the manufacturing process, andthen the transistor, the capacitor, or the like can be transferred tothe substrate 411 or the like. Thus, a transistor, a capacitor, or thelike can be formed over a flexible substrate, for example.

«Substrate 412»

For example, a material that can be used for the substrate 411 can beused for the substrate 412. For example, a light-transmitting materialthat can be used for the substrate 411 can be used for the substrate412. Alternatively, a material having a surface provided with anantireflective film with a thickness of 1 μm or less can be used for thesubstrate 412. Specifically, a stack including three or more, preferablyfive or more, further preferably 15 or more dielectrics can be used forthe substrate 412. This allows reflectivity to be as low as 0.5% orless, preferably 0.08% or less. Alternatively, a material with lowbirefringence that can be used for the substrate 411 can be used for thesubstrate 412.

For example, aluminosilicate glass, tempered glass, chemically temperedglass, sapphire, or the like can be favorably used for the substrate 412that is on the side closer to a user of the display panel. This canprevent breakage or damage of the display panel caused by the use.

For example, a resin film of a cycloolefin polymer (COP), a cycloolefincopolymer (COC), or triacetyl cellulose (TAC) can be favorably used forthe substrate 412. As a result, the weight can be reduced.Alternatively, for example, the display panel can be made less likely tosuffer from damage by dropping or the like.

«Coloring Film 431, Light-blocking Film 630, and Insulating Layer 629»

The coloring film 431, a light-blocking film 630, an insulating layer629, and the like are provided on a surface of the substrate 412 on thesubstrate 411 side.

The coloring film 431 has a function of transmitting light of apredetermined color. That is, the coloring film 431 functions as a colorfilter.

The light-blocking film 630 has a function of suppressing lighttransmission. That is, the light-blocking film 630 functions as a blackmatrix. Specifically, a resin containing a pigment or dye can be usedfor the light-blocking film 630. For example, a resin in which carbonblack is dispersed can be used for the light-blocking film 630.Alternatively, an inorganic compound, an inorganic oxide, a compositeoxide containing a solution of a plurality of inorganic oxides, or thelike can be used for the light-blocking film 630. Specifically, a blackchromium film, a film containing cupric oxide, or a film containingcopper chloride or tellurium chloride can be used for the light-blockingfilm 630.

The insulating layer 629 functions as an overcoat preventing impuritiescontained in the coloring film 431, the light-blocking film 630, and thelike from diffusing into the liquid crystal 423. The insulating layer629 also has a function of reducing unevenness caused by the coloringfilm 431 and the light-blocking film 630.

«Other Components»

A spacer 633 is a columnar spacer obtained by selective etching of aninsulating layer and is provided in order to control the distance (acell gap) between the insulating layer 629 and the insulating layer 624.Alternatively, a spherical spacer may be used.

A glass material such as a glass frit, or a resin material such as aresin that is curable at room temperature such as atwo-component-mixture-type resin, a light curable resin, and athermosetting resin can be used for a sealant 627. A drying agent may becontained in the sealant 627.

If needed, the substrate 412 may be provided with an optical film suchas a polarizing plate, a circularly polarizing plate (including anelliptically polarizing plate), or a retardation plate as appropriate.Furthermore, the polarizing plate or the circularly polarizing plate maybe provided with an anti-reflection film. For example, anti-glaretreatment by which reflected light can be diffused by projections anddepressions on a surface so as to reduce the glare can be performed.

<FIG. 28>

FIG. 28 is a cross-sectional view showing details of the schematiccross-sectional view of the display device 50 illustrated in FIG. 26B.Note that the same portions in FIG. 27 and FIG. 28 are denoted by thesame reference numeral and description thereof is omitted.

FIG. 28 illustrates an example of a display panel including, as adisplay element, a light-emitting element such as an EL element. In thedescription given below, the EL element 463 is an organic EL element.

«EL Element 463»

In FIG. 28, the EL element 463 is electrically connected to thetransistor 601 provided in the pixel 10. Note that the structure of theEL element 463 is not limited to the structure in which the firstelectrode 466, the EL layer 465, and the second electrode 464 arestacked. The structure of the EL element 463 can be changed asappropriate depending on the direction in which light is extracted fromthe EL element 463, or the like.

A partition wall 661 is formed using an organic insulating material oran inorganic insulating material. It is particularly preferable that thepartition wall 661 be formed using a photosensitive resin material tohave an opening over the first electrode 466 so that a side surface ofthe opening slopes with continuous curvature.

The EL layer 465 may be formed as a single layer or a plurality oflayers stacked.

When the EL element 463 has a microcavity structure, light with highcolor purity can be extracted. Furthermore, when a microcavity structureand a color filter are used in combination, the glare can be reduced andvisibility of a display image can be increased.

The first electrode 466 and the second electrode 464 can be formed usinga light-transmitting conductive material such as indium oxide containingtungsten oxide, indium zinc oxide containing tungsten oxide, indiumoxide containing titanium oxide, indium tin oxide, indium tin oxidecontaining titanium oxide, indium zinc oxide, or indium tin oxide towhich silicon oxide is added.

The first electrode 466 and the second electrode 464 can be formed usingone or plural kinds selected from metals such as tungsten (W),molybdenum (Mo), zirconium (Zr), hafnium (Hf), vanadium (V), niobium(Nb), tantalum (Ta), chromium (Cr), cobalt (Co), nickel (Ni), titanium(Ti), platinum (Pt), aluminum (Al), copper (Cu), and silver (Ag); alloysthereof; and nitrides thereof.

The first electrode 466 and the second electrode 464 can be formed usinga conductive composition including a conductive macromolecule (alsoreferred to as a conductive polymer). As the conductive macromolecule, aπ-electron conjugated conductive polymer can be used. For example,polyaniline or a derivative thereof, polypyrrole or a derivativethereof, polythiophene or a derivative thereof, a copolymer of two ormore of aniline, pyrrole, and thiophene or a derivative thereof can begiven.

In order to extract light emitted from the EL element 463 to theoutside, at least one of the first electrode 466 and the secondelectrode 464 is transparent. In FIG. 28, the second electrode 464 ispreferably transparent in order to extract light through the substrate412.

A protective layer may be formed over the second electrode 464 and thepartition wall 661 in order to prevent entry of oxygen, hydrogen,moisture, carbon dioxide, or the like into the EL element 463. For theprotective layer, silicon nitride, silicon nitride oxide, aluminumoxide, aluminum nitride, aluminum oxynitride, aluminum nitride oxide,diamond like carbon (DLC), or the like can be formed. A filler 628 isprovided in a space sealed with the first substrate 411, the secondsubstrate 412, and the sealant 627. It is preferable that the displaypanel be packaged (sealed) with a protective film (such as a laminatefilm or an ultraviolet curable resin film) or a cover member with highair-tightness and little degasification so that the EL element 463 isnot exposed to the outside air, in this manner.

As the filler 628, an ultraviolet curable resin or a thermosetting resincan be used as well as an inert gas such as nitrogen or argon; forexample, polyvinyl chloride (PVC), an acrylic resin, polyimide, an epoxyresin, a silicone resin, polyvinyl butyral (PVB), ethylene vinyl acetate(EVA), or the like can be used. A drying agent may be contained in thefiller 628.

«Other Components»

The coloring film 431, the light-blocking film 630, a wiring 634, awiring 662, the electrode 441 a, the electrode 441 b, an insulatinglayer 663, and the like are provided on the surface of the substrate 412on the substrate 411 side. The wiring 634 is electrically connected to aterminal of the FPC 443 via an anisotropic conductive layer 654.

The wiring 634 and the electrodes 441 a and 441 b are concurrentlyformed using the same conductive material.

If needed, the substrate 412 may be provided with an optical film suchas a polarizing plate, a circularly polarizing plate (including anelliptically polarizing plate), or a retardation plate as appropriate asin the description of FIG. 27. Furthermore, the polarizing plate or thecircularly polarizing plate may be provided with an anti-reflectionfilm. For example, anti-glare treatment by which reflected light can bediffused by projections and depressions on a surface so as to reduce theglare can be performed.

Note that this embodiment can be combined with any of the otherembodiments in this specification as appropriate.

(Embodiment 5)

In this embodiment, a structure example of the source driver IC 64mentioned in the above embodiment is described with reference to FIGS.29A and 29B.

FIGS. 29A and 29B are block diagrams of the source driver IC 64 in thecase where a hybrid element including a reflective element and alight-emitting element is used for the pixel 10.

The source driver IC 64 illustrated in FIG. 29A includes a controlcircuit 801, a driver 802, a frame memory 803, a frame memory 804, agate driver signal generation circuit 806, and a gate driver signalgeneration circuit 807.

The control circuit 801 has a function of receiving a signal from theapplication processor 80 and transmitting the signal to each circuitincluded in the source driver IC 64. Examples of interface standards ofthe signal transmitted from the application processor 80 to the controlcircuit 801 include a mobile industry processor interface (MIPI) and aserial peripheral interface (SPI).

The driver 802 has a function of supplying an image signal to the pixelarray 61.

The frame memory 803 has a function of storing the image signaltemporarily.

The gate driver signal generation circuit 806 and the gate driver signalgeneration circuit 807 have a function of supplying a signal to the gatedriver 62 and the gate driver 63, respectively.

One of the gate driver signal generation circuit 806 and the gate driversignal generation circuit 807 has a function of generating a signal fordriving the reflective element of the pixel 10 and the other of the gatedriver signal generation circuit 806 and the gate driver signalgeneration circuit 807 has a function of generating a signal for drivingthe light-emitting element of the pixel 10.

The source driver IC 64 may also function as the touch sensor IC 72illustrated in FIG. 1. FIG. 29B shows a block diagram in that case.

In the source driver IC 64 illustrated in FIG. 29B, the driver circuit402 and the detection circuit 403 illustrated in FIG. 2 are added to theblock diagram of FIG. 29A. When the touch sensor IC 72 is included inthe source driver IC 64 in this manner, manufacturing costs of thedisplay device can be reduced.

In the case where the driver circuit 402 and the detection circuit 403are included in one IC, those two circuits are preferably apart fromeach other. When the driver circuit 402 is near the detection circuit403, the detection sensitivity of the detection circuit 403 deterioratesby the influence of noise generated by the driver circuit 402 anddetection of a touch becomes difficult in some cases. Therefore, thedriver circuit 402 and the detection circuit 403 are preferablypositioned with a circuit such as the gate driver signal generationcircuit 806 or 807 or the driver 802 provided therebetween.

Here, it is assumed that the gate driver 62 and the gate driver 63 drivethe liquid crystal element and the light-emitting element, respectively.That is, it is assumed that the gate driver signal generation circuit806 generates a signal for driving the liquid crystal element and thegate driver signal generation circuit 807 generates a signal for drivingthe light-emitting element. At this time, the driver circuit 402 and thedetection circuit 403 are preferably near the gate driver signalgeneration circuit 806 and the gate driver signal generation circuit807, respectively.

The drive voltage of a light-emitting element is generally lower thanthat of a liquid crystal element. Thus, the amplitude of a voltageoutput from the gate driver signal generation circuit 807 is lower thanthat of a voltage output from the gate driver signal generation circuit806. It can be said that noise generated by the gate driver signalgeneration circuit 807 is smaller than that generated by the gate driversignal generation circuit 806. Therefore, the detection circuit 403 ispreferably provided at a position that is closer to the gate driversignal generation circuit 807 than to the gate driver signal generationcircuit 806.

Note that this embodiment can be combined with any of the otherembodiments in this specification as appropriate.

(Embodiment 6)

In this embodiment, a display unit 700 that can be used as the displayunit 60 described in the above embodiment is described with reference toFIGS. 30A to 30D, FIGS. 31A and 31B, FIGS. 32A to 32C, FIGS. 33A to 33C,FIG. 34, FIGS. 35A and 35B, FIG. 36, FIGS. 37A to 37C, and FIGS. 38A and38B.

FIGS. 30A to 30D illustrate the structure of the display unit 700. FIG.30A is a projection view of a pixel, and FIG. 30B is an exploded viewillustrating part of the structure of the pixel in FIG. 30A. FIG. 30C isa cross-sectional view that is taken along line Y1-Y2 in FIG. 30A andillustrates part of the structure of the pixel. FIG. 30D is a top viewof the pixel in FIG. 30A.

FIGS. 31A and 31B illustrate the structure of the display unit 700. FIG.31A is a cross-sectional view of the pixel taken along line Y1-Y2 inFIG. 30A. FIG. 31B is a cross-sectional view illustrating part of thestructure of the pixel in FIG. 31A.

FIGS. 32A to 32C illustrate the structure of the display unit 700. FIG.32A is a top view of the display unit 700. FIG. 32B is a top viewillustrating part of the pixel of the display unit 700 in FIG. 32A. FIG.32C is a schematic view illustrating a cross-sectional structure of thedisplay unit 700 in FIG. 32A.

FIGS. 33A to 33C and FIG. 34 are cross-sectional views illustrating thestructure of the display unit 700. FIG. 33A is a cross-sectional viewtaken along line X1-X2 and line X3-X4 in FIG. 32A, and line X5-X6 inFIG. 32B. FIGS. 33B and 33C each illustrate part of FIG. 33A.

FIG. 34 is a cross-sectional view taken along line X7-X8 in FIG. 32B andline X9-X10 in FIG. 32A.

FIGS. 35A and 35B are bottom views each illustrating part of a pixelthat can be used for the display unit 700 illustrated in FIG. 32A.

FIG. 36 is a circuit diagram illustrating the configuration of a pixelcircuit included in the display unit 700.

FIGS. 37A to 37C are top views each illustrating the structure of areflective film of the display unit 700.

<Structure Example 1 of Display Panel>

The display unit 700 described in this embodiment includes a pixel702(i,j) (see FIG. 32A).

«Structure Example 1 of Pixel»

The pixel 702(i,j) includes a functional layer 520, a first displayelement 750(i,j), and a second display element 550(i,j) (see FIG. 32C).

The functional layer 520 includes a pixel circuit 530(i,j). Thefunctional layer 520 includes a region positioned between the firstdisplay element 750(i,j) and the second display element 550(i,j).

The pixel circuit 530(i,j) is electrically connected to the firstdisplay element 750(i,j) and the second display element 550(i,j).

«Structure Example 1 First Display Element 750(i,j)»

The first display element 750(i,j) includes a first electrode 751(i,j),a second electrode 752, a layer 753 containing a liquid crystalmaterial, and a reflective film 751B (see FIG. 30B and FIG. 31A). Thefirst display element 750(i,j) has a function of controlling the lightreflected by the reflective film 751B.

The second electrode 752 is provided such that an electric field in thedirection intersecting the thickness direction of the layer 753containing a liquid crystal material is formed between the secondelectrode 752 and the first electrode 751(i,j) (see FIG. 30B and FIG.31A). For example, the second electrode 752 can have a comb-like shape.In this manner, an electric field in the direction intersecting thethickness direction of the layer 753 containing a liquid crystalmaterial can be formed between the second electrode 752 and the firstelectrode 751(i,j). Alternatively, a display element operating in avertical alignment in-plane-switching (VA-IPS) mode can be used as thefirst display element.

FIG. 38B is an external view of a matrix of the second electrodes 752with a comb-like shape.

The reflective film 751B has a shape that does not block light emittedfrom the second display element 550(i,j) (see FIG. 31A). For example,the reflective film 751B can have a shape including a region 751H wherelight is not blocked. Note that the reflective film 751B has unevennessin the thickness direction. The unevenness in the thickness directioncan be formed with the use of unevenness formed along the shape of thesecond electrode 752, for example. By the reflective film 751B with suchunevenness, incident light can be reflected in various directions. Inother words, incident light can be reflected diffusely. Furthermore, aviewing angle of the first display element 750(i,j) can be increased.

«Structure Example 1 of Second Display Element 550(i,j)»

The second display element 550(i,j) has a function of emitting light andis provided such that display using the second display element can beseen from part of a region where display using the first display element750(i,j) can be seen (see FIG. 31A).

With such a structure, display can be performed by controlling theintensity of light reflected by the reflective film with the use of thefirst display element. Furthermore, display using the first displayelement can be complemented using the second display element.Consequently, a novel display panel with high convenience or highreliability can be provided.

«Structure Example 2 of Pixel»

In the display unit 700 described in this embodiment, the pixel 702(i,j)includes an optical element 560 and a covering film 565.

«Structure Example 1 of Optical Element»

The optical element 560 has a light-transmitting property and includes afirst region 560A, a second region 560B, and a third region 560C (seeFIGS. 30B and 30C and FIG. 31B).

The first region 560A includes a region to which light is supplied. Forexample, the first region 560A receives light from the second displayelement 550(i,j).

The second region 560B includes a region in contact with the coveringfilm 565.

The third region 560C has a function of allowing part of light to beextracted and has an area smaller than or equal to the area of theregion of the first region 560A to which light is supplied.

«Structure Example of Covering Film»

The covering film 565 has light reflectivity and has a function ofreflecting part of light and supplying it to the third region 560C. Forexample, the covering film 565 can reflect light emitted from the seconddisplay element 550(i,j) toward the third region 560C. Specifically,part of light incident on the optical element 560 through the firstregion 560A can be reflected by the covering film 565 in contact withthe second region 560B and extracted from the third region 560C, asshown by a solid arrow (see FIG. 31B).

«Structure Example 2 of First Display Element 750(i,j)»

The reflective film 751B has a shape that does not block light extractedfrom the third region 560C.

With such a structure, display can be performed by controlling theintensity of light reflected by the reflective film with the use of thefirst display element. Alternatively, display using the first displayelement can be complemented using the second display element.Alternatively, the light supplied to the first region can be efficientlyemitted from the third region. Alternatively, the light supplied to thefirst region can be gathered and emitted from the third region. Forexample, when a light-emitting element is used as the second displayelement, the area of the light-emitting element can be larger than thatof the third region. Alternatively, light supplied from thelight-emitting element having an area larger than the area of the thirdregion can be gathered in the third region. Alternatively, the densityof a current flowing through the light-emitting element can be decreasedwhile the intensity of light emitted from the third region ismaintained. Alternatively, the reliability of the light-emitting elementcan be increased. For example, an organic EL element or a light-emittingdiode can be used as the light-emitting element. Consequently, a noveldisplay panel with high convenience or high reliability can be provided.

«Structure Example 3 of Pixel»

The pixel 702(i,j) includes part of the functional layer 520, the firstdisplay element 750(i,j), and the second display element 550(i,j) (seeFIG. 32C).

«Functional Layer 520»

The functional layer 520 includes a first conductive film, a secondconductive film, an insulating film 501C, and the pixel circuit530(i,j). The functional layer 520 includes the optical element 560 andthe covering film 565 (see FIG. 33A). The pixel circuit 530(i,j)includes a transistor M, for example.

The functional layer 520 includes a region positioned between the firstdisplay element 750(i,j) and the second display element 550(i,j) (seeFIG. 33C). The region positioned between the first display element750(i,j) and the second display element 550(i,j) has a thickness of lessthan 30 μm, preferably less than 10 μm, further preferably less than 5μm.

In this manner, the second display element 550(i,j) can be close to thefirst display element 750(i,j). Parallax between display using the firstdisplay element 750(i,j) and display using the second display element550(i,j) can be reduced. Display using an adjacent pixel (e.g., a pixel702(i,j+1)) can be inhibited from being disturbed by display using thesecond display element 550(i,j). The color of display using an adjacentpixel (e.g., the pixel 702(i,j+1)) and the color of display using thesecond display element 550(i,j) can be inhibited from being mixed. Theattenuation of light emitted by the second display element 550(i,j) canbe inhibited. The weight of the display panel can be reduced. Thethickness of the display panel can be reduced. The display panel iseasily bendable.

The functional layer 520 includes an insulating film 528, an insulatingfilm 521A, an insulating film 521B, an insulating film 518, and aninsulating film 516.

«Pixel Circuit»

The pixel circuit 530(i,j) has a function of driving the first displayelement 750(i,j) and the second display element 550(i,j) (see FIG. 36).

Thus, the first display element and the second display element thatdisplays an image by a method different from that of the first displayelement can be driven using pixel circuits that can be formed in thesame process. Specifically, a reflective display element is used as thefirst display element, whereby power consumption can be reduced. Animage with high contrast can be favorably displayed in an environmentwith bright external light. An image can be favorably displayed in adark environment with the use of the second display element which emitslight. With the insulating film, impurity diffusion between the firstdisplay element and the second display element or between the firstdisplay element and the pixel circuit can be inhibited. Consequently, anovel display device with high convenience or high reliability can beprovided.

A switch, a transistor, a diode, a resistor, an inductor, a capacitor,or the like can be used in the pixel circuit 530(i,j).

For example, one or a plurality of transistors can be used as a switch.Alternatively, a plurality of transistors connected in parallel, inseries, or in combination of parallel connection and series connectioncan be used as a switch.

For example, the pixel circuit 530(i,j) is electrically connected to asignal line S1(j), a signal line S2(j), a scan line G1(i), a scan lineG2(i), a wiring CSCOM, and a conductive film ANO (see FIG. 36). Aconductive film 512A is electrically connected to the signal line S1(j)(see FIG. 34 and FIG. 36).

The pixel circuit 530(i,j) includes a switch SW1 and a capacitor C11(see FIG. 36).

The pixel circuit 530(i,j) includes a switch SW2, the transistor M, anda capacitor C12.

For example, a transistor including a gate electrode electricallyconnected to the scan line G1(i) and a first electrode electricallyconnected to the signal line S1(j) can be used as the switch SW1.

The capacitor C11 includes a first electrode electrically connected to asecond electrode of the transistor used as the switch SW1, and a secondelectrode electrically connected to the wiring CSCOM.

For example, a transistor including a gate electrode electricallyconnected to the scan line G2(i) and a first electrode electricallyconnected to the signal line S2(j) can be used as the switch SW2.

The transistor M includes a gate electrode electrically connected to thesecond electrode of the transistor used as the switch SW2 and includes afirst electrode electrically connected to the conductive film ANO.

Note that a transistor including a conductive film provided such that asemiconductor film is interposed between a gate electrode and theconductive film can be used as the transistor M. For example, as theconductive film, a conductive film electrically connected to a wiringthat can supply the same potential as that of the gate electrode of thetransistor M can be used.

The capacitor C12 includes a first electrode electrically connected to asecond electrode of the transistor used as the switch SW2 and a secondelectrode electrically connected to the first electrode of thetransistor M.

Note that the first electrode of the first display element 750(i,j) iselectrically connected to the second electrode of the transistor used asthe switch SW1. The second electrode 752 of the first display element750(i,j) is electrically connected to a wiring VCOM1. This enables thefirst display element 750 to be driven.

An electrode 551(i,j) and an electrode 552 of the second display element550(i,j) are electrically connected to a second electrode of thetransistor M and a conductive film VCOM2, respectively. This enables thesecond display element 550(i,j) to be driven.

«Insulating Film 501C»

The insulating film 501C includes a region positioned between the firstconductive film and the second conductive film and has an opening 591A(see FIG. 34).

«First Conductive Film»

The first conductive film is electrically connected to the first displayelement 750(i,j). Specifically, the first conductive film iselectrically connected to the electrode 751(i,j) of the first displayelement 750(i,j). The electrode 751(i,j) can be used as the firstconductive film.

«Second Conductive Film»

The second conductive film includes a region overlapping with the firstconductive film. The second conductive film is electrically connected tothe first conductive film through the opening 591A. For example, aconductive film 512B can be used as the second conductive film.

Note that the first conductive film electrically connected to the secondconductive film in the opening 591A formed in the insulating film 501Ccan be referred to as a through electrode.

The second conductive film is electrically connected to the pixelcircuit 530(i,j). For example, a conductive film that functions as asource electrode or a drain electrode of a transistor used as the switchSW1 of the pixel circuit 530(i,j) can be used as the second conductivefilm.

«Structure Example 2 of Second Display Element 550(i,j)»

The second display element 550(i,j) is electrically connected to thepixel circuit 530(i,j) (see FIG. 33A and FIG. 36). The second displayelement 550(i,j) has a function of emitting light toward the functionallayer 520. The second display element 550(i,j) has a function ofemitting light toward the insulating film 501C, for example.

The second display element 550(i,j) is provided such that display usingthe second display element 550(i,j) can be seen from part of a regionwhere display using the first display element 750(i,j) can be seen. Forexample, dashed arrows shown in FIG. 34 denote the directions in whichexternal light is incident on and reflected by the first display element750(i,j) that displays image data by controlling the intensity ofexternal light reflection. In addition, a solid arrow shown in FIG. 33Adenotes the direction in which the second display element 550(i,j) emitslight to part of the region where display using the first displayelement 750(i,j) can be seen.

Accordingly, display using the second display element can be seen frompart of the region where display using the first display element can beseen. Alternatively, users can see display without changing the attitudeor the like of the display panel. Alternatively, an object colorexpressed by light reflected by the first display element and a lightsource color expressed by light emitted from the second display elementcan be mixed. Alternatively, an object color and a light source colorcan be used to display an image like a painting. Thus, a novel displaypanel with high convenience or high reliability can be provided.

For example, the second display element 550(i,j) includes the electrode551(i,j), the electrode 552, and a layer 553(j) containing alight-emitting material (see FIG. 33A).

The electrode 552 includes a region overlapping with the electrode551(i,j).

The layer 553(j) containing a light-emitting material includes a regionpositioned between the electrode 551(i,j) and the electrode 552.

The electrode 551(i,j) is electrically connected to the pixel circuit530(i,j) at a connection portion 522. The electrode 552 is electricallyconnected to the conductive film VCOM2 (see FIG. 36).

«Insulating Films 521, 528, 518, and 516»

An insulating film 521 includes a region positioned between the pixelcircuit 530(i,j) and the second display element 550(i,j) (see FIG. 33A).

For example, a laminated film can be used as the insulating film 521.For example, a stack including the insulating film 521A, the insulatingfilm 521B, and an insulating film 521C can be used as the insulatingfilm 521.

The insulating film 528 includes a region positioned between theinsulating film 521 and the substrate 570 and has an opening in a regionoverlapping with the second display element 550(i,j). The insulatingfilm 528 that is along the edge of the electrode 551(i,j) can avoid ashort circuit between the electrode 551(i,j) and the electrode 552.

Note that a single-layer film or a laminated film can be used as theinsulating film 518. For example, an insulating film 518A and aninsulating film 518B can be used for the insulating film 518.Alternatively, for example, an insulating film 518A1 and an insulatingfilm 518A2 can be used for the insulating film 518.

The insulating film 518 includes a region positioned between theinsulating film 521 and the pixel circuit 530(i,j).

The insulating film 516 includes a region positioned between theinsulating film 518 and the pixel circuit 530(i,j).

Furthermore, the display unit 700 can include an insulating film 501B.The insulating film 501B has an opening 592B (see FIG. 33A).

The opening 592B includes a region overlapping with a conductive film511B.

<Structure Example 2 of Display Panel>

The display unit 700 described in this embodiment can include aplurality of pixels having functions of representing colors withdifferent hues. Furthermore, colors with hues that cannot be representedby the plurality of pixels capable of representing colors with differenthues can be represented by additive color mixing with the use of thepixels.

Note that when a plurality of pixels capable of representing colors withdifferent hues are used for color mixture, each of the pixels can bereferred to as a subpixel. In addition, a set of subpixels can bereferred to as a pixel. Specifically, the pixel 702(i,j) can be referredto as a subpixel, and the pixel 702(i,j) the pixel 702(i,j+1), and apixel 702(i,j+2) can be collectively referred to as a pixel 703(i,k)(see FIG. 38A).

For example, a subpixel that represents blue, a subpixel that representsgreen, and a subpixel that represents red can be collectively used asthe pixel 703(i,k).

Alternatively, for example, a subpixel that represents cyan, a subpixelthat represents magenta, and a subpixel that represents yellow can becollectively used as the pixel 703(i,k).

Alternatively, for example, the above set to which a subpixel thatrepresents white is added can be used as the pixel.

Alternatively, for example, a set of the following subpixels can be usedas the pixel 703(i,k): a subpixel including the first display element750(i,j) that represents cyan and the second display element 550(i,j)that represents blue; a subpixel including a first display element750(i,j+1) that represents yellow and a second display element550(i,j+1) that represents green; and a subpixel including a firstdisplay element 750(i,j+2) that represents magenta and a second displayelement 550(i,j+2) that represents red. This allows bright display usingthe first display elements 750(i,j) to 750(i,j+2) or clear display usingthe second display elements 550(i,j) to 550(i,j+2).

<Structure Example 3 of Display Panel>

Moreover, the display unit 700 described in this embodiment includes afunctional layer 720, a terminal 519B, the substrate 570, a substrate770, a bonding layer 505, a sealing material 705, a structure body KB1,a functional film 770P, a functional film 770D, and the like (see FIG.33A or FIG. 34).

«Functional Layer 720»

The display panel described in this embodiment includes the functionallayer 720. The functional layer 720 includes a region positioned betweenthe substrate 770 and the insulating film 501C. The functional layer 720includes a light-blocking film BM, an insulating film 771, and acoloring film CF1 (see FIG. 33A or FIG. 34).

The light-blocking film BM has an opening in a region overlapping withthe first display element 750(i,j).

The coloring film CF1 includes a region positioned between the substrate770 and the first display element 750(i,j). Note that a bonding layer770B can be provided between the functional layer 720 and the substrate770. The bonding layer 770B has a function of bonding the functionallayer 720 and the substrate 770.

The insulating film 771 includes a region between the coloring film CF1and the layer 753 containing a liquid crystal material or a regionbetween the light-blocking film BM and the layer 753 containing a liquidcrystal material. The insulating film 771 can reduce unevenness due tothe thickness of the coloring film CF1. Alternatively, impurities can beprevented from being diffused from the light-blocking film BM, thecoloring film CF1, or the like to the layer 753 containing a liquidcrystal material.

Note that a single-layer film or a laminated film can be used for theinsulating film 771. For example, an insulating film 771A and aninsulating film 771B can be used for the insulating film 771.

«Terminal 519B»

The display panel described in this embodiment includes the terminal519B (see FIG. 33A).

The terminal 519B includes the conductive film 511B. The terminal 519Bis electrically connected to the signal line S1(j), for example.

«Substrate 570 and Substrate 770»

In addition, the display panel described in this embodiment includes thesubstrate 570 and the substrate 770.

The substrate 770 includes a region overlapping with the substrate 570.The substrate 770 includes a region positioned such that the functionallayer 520 is sandwiched between the substrate 770 and the substrate 570.

The substrate 770 includes a region overlapping with the first displayelement 750(i,j). For example, a material with low birefringence can beused for the region.

«Bonding Layer 505, Sealing Material 705, and Structure Body KB1»

The display panel described in this embodiment includes the bondinglayer 505, the sealing material 705, and the structure body KB1.

The bonding layer 505 includes a region positioned between thefunctional layer 520 and the substrate 570, and has a function ofbonding the functional layer 520 and the substrate 570 to each other.

The sealing material 705 includes a region positioned between thefunctional layer 520 and the substrate 770, and has a function ofbonding the functional layer 520 and the substrate 770 to each other.

The structure body KB1 has a function of providing a certain spacebetween the functional layer 520 and the substrate 770.

«Functional Films 770PA, 770PB, and 770D»

The display panel described in this embodiment includes a functionalfilm 770PA, a functional film 770PB, and the functional film 770D.

The functional films 770PA and 770PB each include a region overlappingwith the first display element 750(i,j).

The functional film 770D includes a region overlapping with the firstdisplay element 750(i,j). The functional film 770D is provided such thatthe substrate 770 lies between the functional film 770D and the firstdisplay element 750(i,j). Thus, for example, light reflected by thefirst display element 750(i,j) can be diffused.

<Example of Components>

Components of the display unit 700 are described below.

«Substrate 570»

The substrate 570 or the like can be formed using a material having heatresistance high enough to withstand heat treatment in the manufacturingprocess. For example, a material with a thickness greater than or equalto 0.1 mm and less than or equal to 0.7 mm can be used for the substrate570. Specifically, a material polished to a thickness of approximately0.1 mm can be used.

For example, a large-sized glass substrate having any of the followingsizes can be used as the substrate 570 or the like: the 6th generation(1500 mm×1850 mm), the 7th generation (1870 mm×2200 mm), the 8thgeneration (2200 mm×2400 mm), the 9th generation (2400 mm×2800 mm), andthe 10th generation (2950 mm×3400 mm). Thus, a large-sized displaydevice can be manufactured.

For the substrate 570 or the like, an organic material, an inorganicmaterial, a composite material of an organic material and an inorganicmaterial, or the like can be used. For example, an inorganic materialsuch as glass, ceramic, or a metal can be used for the substrate 570 orthe like.

Specifically, non-alkali glass, soda-lime glass, potash glass, crystalglass, aluminosilicate glass, tempered glass, chemically tempered glass,quartz, sapphire, or the like can be used for the substrate 570 or thelike. Specifically, an inorganic oxide film, an inorganic nitride film,an inorganic oxynitride film, or the like can be used for the substrate570 or the like. For example, a silicon oxide film, a silicon nitridefilm, a silicon oxynitride film, an aluminum oxide film, or the like canbe used for the substrate 570 or the like. Stainless steel, aluminum, orthe like can be used for the substrate 570 or the like.

For example, a single crystal semiconductor substrate or apolycrystalline semiconductor substrate of silicon or silicon carbide, acompound semiconductor substrate of silicon germanium or the like, or anSOI substrate can be used for the substrate 570 or the like. Thus, asemiconductor element can be provided over the substrate 570 or thelike.

For example, an organic material such as a resin, a resin film, orplastic can be used for the substrate 570 or the like. Specifically, aresin film or a resin plate of polyester, polyolefin, polyamide,polyimide, polycarbonate, an acrylic resin, or the like can be used forthe substrate 570 or the like.

For example, a composite material formed by attaching a metal plate, athin glass plate, or a film of an inorganic material to a resin film orthe like can be used for the substrate 570 or the like. For example, acomposite material formed by dispersing a fibrous or particulate metal,glass, inorganic material, or the like into a resin film can be used forthe substrate 570 or the like. For example, a composite material formedby dispersing a fibrous or particulate resin, organic material, or thelike into an inorganic material can be used for the substrate 570 or thelike.

A single-layer material or a material obtained by stacking a pluralityof layers can be used for the substrate 570 or the like. For example, alayered material in which a base, an insulating film that preventsdiffusion of impurities contained in the base, and the like are stackedcan be used for the substrate 570 or the like. Specifically, a materialobtained by stacking glass and one or a plurality of films that areselected from a silicon oxide layer, a silicon nitride layer, a siliconoxynitride layer, and the like and that prevent diffusion of impuritiescontained in the glass can be used for the substrate 570 or the like.Alternatively, a material obtained by stacking a resin and a film thatprevents diffusion of impurities that penetrate the resin, such as asilicon oxide film, a silicon nitride film, or a silicon oxynitridefilm, can be used for the substrate 570 or the like.

Specifically, a resin film, a resin plate, a layered material, or thelike of polyester, polyolefin, polyamide, polyimide, polycarbonate, anacrylic resin, or the like can be used for the substrate 570 or thelike.

Specifically, a material including polyester, polyolefin, polyamide(e.g., nylon or aramid), polyimide, polycarbonate, polyurethane, anacrylic resin, an epoxy resin, or a resin having a siloxane bond, suchas silicone can be used for the substrate 570 or the like.

Specifically, polyethylene terephthalate (PET), polyethylene naphthalate(PEN), polyethersulfone (PES), an acrylic resin, or the like can be usedfor the substrate 570 or the like. Alternatively, a cycloolefin polymer(COP), a cycloolefin copolymer (COC), or the like can be used.

Alternatively, paper, wood, or the like can be used for the substrate570 or the like.

For example, a flexible substrate can be used for the substrate 570 orthe like.

Note that a transistor, a capacitor, or the like can be directly formedon the substrate. Alternatively, a transistor, a capacitor, or the likecan be formed over a substrate which is for use in the manufacturingprocess and can withstand heat applied in the manufacturing process, andthen the transistor, the capacitor, or the like can be transferred tothe substrate 570 or the like. Thus, a transistor, a capacitor, or thelike can be formed over a flexible substrate, for example.

«Substrate 770»

For example, a material that can be used for the substrate 570 can beused for the substrate 770. For example, a light-transmitting materialthat can be used for the substrate 570 can be used for the substrate770. Alternatively, a material having a surface provided with anantireflective film with a thickness of 1 μm or less can be used for thesubstrate 770. Specifically, a stack including three or more, preferablyfive or more, more preferably 15 or more dielectrics can be used for thesubstrate 770. This allows reflectivity to be as low as 0.5% or less,preferably 0.08% or less. Alternatively, a material with lowbirefringence that can be used for the substrate 570 can be used for thesubstrate 770.

For example, aluminosilicate glass, tempered glass, chemically temperedglass, sapphire, or the like can be favorably used for the substrate 770that is on the side closer to a user of the display panel. This canprevent breakage or damage of the display panel caused by the use.

For example, a resin film of a cycloolefin polymer (COP), a cycloolefincopolymer (COC), or triacetyl cellulose (TAC) can be favorably used forthe substrate 770. As a result, the weight can be reduced.Alternatively, for example, the display panel can be made less likely tosuffer from damage by dropping or the like.

A material with a thickness greater than or equal to 0.1 mm and lessthan or equal to 0.7 mm can be used for the substrate 770, for example.Specifically, a substrate polished to be reduced in the thickness can beused. In that case, the functional film 770D can be close to the firstdisplay element 750(i,j). As a result, image blur can be reduced, and animage can be displayed clearly.

«Structure Body KB1»

The structure body KB1 or the like can be formed using an organicmaterial, an inorganic material, or a composite material of an organicmaterial and an inorganic material, for example. Accordingly, apredetermined space can be provided between components between which thestructure body KB1 and the like are provided.

Specifically, for the structure body KB1, polyester, polyolefin,polyamide, polyimide, polycarbonate, polysiloxane, an acrylic resin, orthe like, or a composite material of a plurality of resins selected fromthese can be used. Alternatively, a photosensitive material may be used.

«Sealing Material 705»

For the sealing material 705 or the like, an inorganic material, anorganic material, a composite material of an inorganic material and anorganic material, or the like can be used.

For example, an organic material such as a thermally fusible resin or acurable resin can be used for the sealing material 705 or the like.

For example, an organic material such as a reactive curable adhesive, alight curable adhesive, a thermosetting adhesive, and/or an anaerobicadhesive can be used for the sealing material 705 or the like.

Specifically, an adhesive containing an epoxy resin, an acrylic resin, asilicone resin, a phenol resin, a polyimide resin, an imide resin, apolyvinyl chloride (PVC) resin, a polyvinyl butyral (PVB) resin, or anethylene vinyl acetate (EVA) resin, or the like can be used for thesealing material 705 or the like.

«Bonding Layers 505 and 770B»

For example, any of the materials that can be used for the sealingmaterial 705 can be used for the bonding layer 505 or the bonding layer770B.

«Insulating Film 521»

For example, an insulating inorganic material, an insulating organicmaterial, an insulating composite material containing an inorganicmaterial and an organic material can be used for the insulating film 521or the like.

Specifically, for example, an inorganic oxide film, an inorganic nitridefilm, an inorganic oxynitride film, or a material obtained by stackingany of these films can be used as the insulating film 521 or the like.For example, a film including any of a silicon oxide film, a siliconnitride film, a silicon oxynitride film, and an aluminum oxide film, ora film including a layered material obtained by stacking any of thesefilms can be used as the insulating film 521 or the like.

Specifically, for the insulating film 521 or the like, polyester,polyolefin, polyamide, polyimide, polycarbonate, polysiloxane, anacrylic resin, or the like, or a laminated or composite material of aplurality of kinds of resins selected from these can be used.Alternatively, a photosensitive material may be used. Note thatpolyimide is excellent in the following properties: thermal stability,an insulating property, toughness, a low dielectric constant, a lowcoefficient of thermal expansion, and a low hygroscopic property, forexample. Accordingly, in particular, polyimide can be suitably used forthe insulating film 521 or the like.

Thus, steps due to various components overlapping with the insulatingfilm 521, for example, can be reduced.

«Optical Element 560»

The optical element 560 has an optical axis Z (see FIG. 30C). Theoptical axis Z passes through the center of the region of the firstregion 560A to which visible light is supplied and the center of thethird region 560C. The second region 560B includes an inclined portionwith an inclination θ of 45° or more, preferably 75° or more and 85° orless, with respect to a plane orthogonal to the optical axis Z. Forexample, the second region 560B illustrated in the drawing entirely hasan inclination of approximately 60° with respect to the plane orthogonalto the optical axis Z.

The inclined portion of the second region 560B is provided withingreater than or equal to 0.05 μm and less than or equal to 0.2 μm of theend of the region of the first region 560A to which visible light issupplied. Note that in the case where the second display element550(i,j) is in contact with the first region 560A, the region of thefirst region 560A to which visible light is supplied has the same areaas the region of the second display element 550(i,j) that can supplyvisible light. For example, the inclined portion of the second region560B illustrated in the drawing is positioned at a distance d from theend of the region of the first region to which visible light issupplied.

The region of the first region 560A to which visible light is suppliedhas an area larger than 10% of the area of the pixel 702(i,j) (see FIG.30D).

The third region 560C has an area smaller than or equal to 10% of thearea of the pixel 702(i,j).

The reflective film 751B has an area larger than or equal to 70% of thearea of the pixel 702(i,j).

The sum of the area of the region of the first region 560A to whichvisible light is supplied and the area of the reflective film 751B islarger than the area of the pixel 702(i,j).

For example, a rectangular pixel 27 μm wide and 81 μm long has an areaof 2187 μm². In the case of such a pixel, the region of the first region560A to which visible light is supplied has an area of 324 μm². Thethird region 560C has an area of 81 ∞m², and the reflective film 751Bhas an area of 1894 μm².

In this structure, the area of a region of the first region 560A towhich visible light is supplied is approximately 14.8% of the area ofthe pixel.

The area of the reflective film 751B is approximately 86.6% of the areaof the pixel.

The sum of the area of the region of the first region 560A to whichvisible light is supplied and the area of the reflective film 751B is2218 μm².

Thus, in the second region, light incident through the first region atvarious angles can be gathered. Consequently, a novel display panel withhigh convenience or high reliability can be provided.

Note that a plurality of materials can be used for the optical element560. For example, a plurality of materials selected such that adifference between their refractive indices is 0.2 or less can be usedfor the optical element 560. Thus, reflection or scattering of light inthe optical element or loss of light can be inhibited.

The optical element 560 can have any of various shapes. For example, theshape of a section orthogonal to the optical axis of the optical element560 can be a circle or a polygon. The second region 560B of the opticalelement 560 can have a flat surface or a curved surface.

«Covering Film 565»

A single-layer film or a laminated film can be used as the covering film565. For example, a stack including a light-transmitting film and areflective film can be used for the covering film 565.

For example, an inorganic material such as an oxide film, a fluoridefilm, or a sulfide film can be used for the light-transmitting film.

For example, a metal can be used for the reflective film. Specifically,a material containing silver can be used for the covering film 565. Forexample, a material containing silver, palladium, and the like or amaterial containing silver, copper, and the like can be used for thereflective film. Alternatively, a multilayer film of dielectrics can beused for the reflective film.

«Insulating Film 528»

For example, any of the materials that can be used for the insulatingfilm 521 can be used for the insulating film 528 or the like.Specifically, a 1-μm-thick polyimide-containing film can be used as theinsulating film 528.

«Insulating Film 501B»

For example, a material that can be used for the insulating film 521 canbe used for the insulating film 501B. For example, a material having afunction of supplying hydrogen can be used for the insulating film 501B.

Specifically, a material obtained by stacking a material containingsilicon and oxygen and a material containing silicon and nitrogen can beused for the insulating film 501B. For example, a material having afunction of releasing hydrogen by heating or the like to supply thehydrogen to another component can be used for the insulating film 501B.Specifically, a material having a function of releasing hydrogen takenin the manufacturing process, by heating or the like, to supply thehydrogen to another component can be used for the insulating film 501B.

For example, a film containing silicon and oxygen that is formed by achemical vapor deposition method using silane or the like as a sourcegas can be used as the insulating film 501B.

Specifically, a material obtained by stacking a material containingsilicon and oxygen and having a thickness greater than or equal to 200nm and less than or equal to 600 nm and a material containing siliconand nitrogen and having a thickness of approximately 200 nm can be usedfor the insulating film 501B.

«Insulating Film 501C»

For example, any of the materials that can be used for the insulatingfilm 521 can be used for the insulating film 501C. Specifically, amaterial containing silicon and oxygen can be used for the insulatingfilm 501C. Thus, diffusion of impurities into the pixel circuit, thesecond display element, or the like can be inhibited.

For example, a 200-nm-thick film containing silicon, oxygen, andnitrogen can be used as the insulating film 501C.

«Wiring, Terminal, and Conductive Film»

A conductive material can be used for the wiring or the like.Specifically, the conductive material can be used for the signal lineS1(j), the signal line S2(j), the scan line G1(i), the scan line G2(i),the wiring CSCOM, the conductive film ANO, the terminal 519B, theconductive film 511B, or the like.

For example, an inorganic conductive material, an organic conductivematerial, a metal, conductive ceramics, or the like can be used for thewiring or the like.

Specifically, a metal element selected from aluminum, gold, platinum,silver, copper, chromium, tantalum, titanium, molybdenum, tungsten,nickel, iron, cobalt, palladium, and manganese can be used for thewiring or the like. Alternatively, an alloy containing any of theabove-described metal elements, or the like can be used for the wiringor the like. In particular, an alloy of copper and manganese is suitablyused in microfabrication using a wet etching method.

Specifically, any of the following structures can be used for the wiringor the like: a two-layer structure in which a titanium film is stackedover an aluminum film, a two-layer structure in which a titanium film isstacked over a titanium nitride film, a two-layer structure in which atungsten film is stacked over a titanium nitride film, a two-layerstructure in which a tungsten film is stacked over a tantalum nitridefilm or a tungsten nitride film, a three-layer structure in which atitanium film, an aluminum film, and a titanium film are stacked in thisorder, and the like.

Specifically, a conductive oxide, such as indium oxide, indium tinoxide, indium zinc oxide, zinc oxide, or zinc oxide to which gallium isadded, can be used for the wiring or the like.

Specifically, a film containing graphene or graphite can be used for thewiring or the like.

For example, a film containing graphene oxide is formed and subjected toreduction, whereby a film containing graphene can be formed. As areducing method, a method with application of heat, a method using areducing agent, or the like can be employed.

A film containing a metal nanowire can be used for the wiring or thelike, for example. Specifically, a nanowire containing silver can beused.

Specifically, a conducting polymer can be used for the wiring or thelike.

Note that the terminal 519B can be electrically connected to a flexibleprinted circuit FPC1 with the use of a conductive material ACF1, forexample.

«First Conductive Film and Second Conductive Film»

For example, any of the materials that can be used for the wiring or thelike can be used for the first conductive film or the second conductivefilm.

The electrode 751(i,j), the wiring, or the like can be used for thefirst conductive film.

The conductive film 512B functioning as the source electrode or thedrain electrode of the transistor that can be used for the switch SW1,the wiring, or the like can be used for the second conductive film.

«First Display Element 750(i,j)»

For example, a display element having a function of controllingtransmission or reflection of light can be used as the first displayelement 750(i,j). For example, a combined structure of a liquid crystalelement and a polarizing plate, a MEMS shutter display element, a MEMSoptical coherence display element, or the like can be used. The use of areflective display element can reduce the power consumption of thedisplay panel. For example, a display element using a microcapsulemethod, an electrophoretic method, an electrowetting method, or the likecan be used as the first display element 750(i,j). Specifically, areflective liquid crystal display element can be used as the firstdisplay element 750(i,j).

For example, a liquid crystal element driven in any of the followingdriving modes can be used: an in-plane switching (IPS) mode, a twistednematic (TN) mode, a fringe field switching (FFS) mode, an axiallysymmetric aligned micro-cell (ASM) mode, an optically compensatedbirefringence (OCB) mode, a ferroelectric liquid crystal (FLC) mode, anantiferroelectric liquid crystal (AFLC) mode, and the like.

Alternatively, a liquid crystal element that can be driven by, forexample, a vertical alignment (VA) mode such as a multi-domain verticalalignment (MVA) mode, a patterned vertical alignment (PVA) mode, anelectrically controlled birefringence (ECB) mode, a continuous pinwheelalignment (CPA) mode, or an advanced super view (ASV) mode can be used.

The first display element 750(i,j) includes the first electrode, thesecond electrode, and the layer containing a liquid crystal material.The layer containing a liquid crystal material contains a liquid crystalmaterial whose alignment can be controlled by voltage applied betweenthe first electrode and the second electrode. For example, the alignmentof the liquid crystal material can be controlled by an electric field inthe thickness direction (also referred to as the vertical direction) oran electric field in the direction that intersects the verticaldirection (also referred to as the horizontal direction or the diagonaldirection) of the layer containing a liquid crystal material.

«Layer 753 Containing Liquid Crystal Material»

For example, thermotropic liquid crystal, low-molecular liquid crystal,high-molecular liquid crystal, polymer dispersed liquid crystal,ferroelectric liquid crystal, anti-ferroelectric liquid crystal, or thelike can be used for the layer containing a liquid crystal material.Alternatively, a liquid crystal material which exhibits a cholestericphase, a smectic phase, a cubic phase, a chiral nematic phase, anisotropic phase, or the like can be used. Alternatively, a liquidcrystal material which exhibits a blue phase can be used.

For example, a negative liquid crystal material can be used for thelayer containing a liquid crystal material.

For example, a liquid crystal material having a resistivity of greaterthan or equal to 1.0×10¹³ Ω·cm, preferably greater than or equal to1.0×10¹⁴ Ω·cm, further preferably greater than or equal to 1.0×10¹⁵Ω·cm, is preferably used for the layer 753 containing a liquid crystalmaterial. This can suppress a variation in the transmittance of thefirst display element 750(i,j). Alternatively, flickering of the firstdisplay element 750(i,j) can be suppressed. Alternatively, the rewritingfrequency of the first display element 750(i,j) can be reduced.

«Electrode 751(i,j)»

For example, the material that is used for the wiring or the like can beused for the electrode 751(i,j). Specifically, a reflective film can beused for the electrode 751(i,j). For example, a material in which alight-transmitting conductive film and a reflective film having anopening are stacked can be used for the electrode 751(i,j).

«Reflective Film»

For example, a material that reflects visible light can be used for thereflective film. Specifically, a material containing silver can be usedfor the reflective film. For example, a material containing silver,palladium, and the like or a material containing silver, copper, and thelike can be used for the reflective film.

The reflective film reflects light that passes through the layer 753containing a liquid crystal material, for example. This allows the firstdisplay element 750 to serve as a reflective liquid crystal element.Alternatively, for example, a material with unevenness on its surfacecan be used for the reflective film. In that case, incident light can bereflected in various directions so that a white image can be displayed.

The reflective film has a shape including the region 751H where lightemitted from the second display element 550(i,j) is not blocked (seeFIGS. 37A to 37C).

For example, the reflective film can have one or more openings.Specifically, the region 751H may have a polygonal shape, a quadrangularshape, an elliptical shape, a circular shape, a cross-like shape, or thelike. The region 751H may alternatively have a stripe shape, a slit-likeshape, or a checkered pattern.

If the ratio of the total area of the region 751H to the total area ofthe reflective film is too large, an image displayed using the firstdisplay element 750(i,j) is dark.

If the ratio of the total area of the region 751H to the total area ofthe reflective film is too small, an image displayed using the seconddisplay element 550(i,j) is dark. The reliability of the second displayelement 550(i,j) may be degraded.

For example, the region 751H provided in the pixel 702(i,j+1) is notprovided on a line that extends in the row direction (the directionindicated by the arrow R1 in the drawing) through the region 751Hprovided in the pixel 702(i,j) (see FIG. 37A). Alternatively, forexample, the region 751H provided in a pixel 702(i+1j) is not providedon a line that extends in the column direction (the direction indicatedby the arrow C1 in the drawing) through the region 751H provided in thepixel 702(i,j) (see FIG. 37B).

For example, the region 751H provided in the pixel 702(i,j+2) isprovided on a line that extends in the row direction through the region751H provided in the pixel 702(i,j) (see FIG. 37A). In addition, theregion 751H provided in the pixel 702(i,j+1) is provided on a line thatis perpendicular to the above line between the region 751H provided inthe pixel 702(i,j) and the region 751H provided in the pixel 702(i,j+2).

Alternatively, for example, the region 751H provided in a pixel702(i+2j) is provided on a line that extends in the column directionthrough the region 751H provided in the pixel 702(i,j) (see FIG. 37B).In addition, for example, the region 751H provided in the pixel702(i+1j) is provided on a line that is perpendicular to the above linebetween the region 751H provided in the pixel 702(i,j) and the region751H provided in the pixel 702(i+2j).

When the second display elements are provided in the above manner tooverlap with the regions where light is not blocked, the second displayelement of one pixel adjacent to another pixel can be apart from asecond display element of the another pixel. A display element thatdisplays color different from that displayed from the second displayelement of one pixel can be provided as the second display element ofanother pixel adjacent to the one pixel. The difficulty in arranging aplurality of display elements that represent different colors adjacentto each other can be lowered. Thus, a novel display panel with highconvenience or high reliability can be provided.

The reflective film can have a shape in which an end portion is cut offso as to form the region 751H (see FIG. 37C). Specifically, thereflective film can have a shape in which an end portion is cut off soas to be shorter in the column direction (the direction indicated by thearrow C1 in the drawing).

«Electrode 752»

For example, a material that can be used for the wiring or the like canbe used for the electrode 752. For example, a material that has alight-transmitting property selected from materials that can be used forthe wiring or the like can be used for the electrode 752.

For example, a conductive oxide, a metal film thin enough to transmitlight, a metal nanowire, or the like can be used for the electrode 752.

Specifically, a conductive oxide containing indium can be used for theelectrode 752. Alternatively, a metal thin film with a thickness greaterthan or equal to 1 nm and less than or equal to 10 nm can be used forthe electrode 752. Alternatively, a metal nanowire containing silver canbe used for the electrode 752.

Specifically, indium oxide, indium tin oxide, indium zinc oxide, zincoxide, zinc oxide to which gallium is added, zinc oxide to whichaluminum is added, or the like can be used for the electrode 752.

«Alignment Films AF1 and AF2»

Alignment films AF1 and AF2 can be formed using a material containingpolyimide or the like, for example. Specifically, a material formed byrubbing treatment or an optical alignment technique such that a liquidcrystal material has alignment in a predetermined direction can be used.

For example, a film containing soluble polyimide can be used for thealignment film AF1 or AF2. In that case, the temperature required informing the alignment film AF1 or AF2 can be low. As a result, damage toother components caused when the alignment film AF1 or AF2 is formed canbe reduced.

«Coloring Film CF1»

The coloring film CF1 can be formed using a material transmitting lightof a certain color and can thus be used for a color filter or the like.

For example, a material that transmits blue light, green light, or redlight can be used for the coloring film CF1. In that case, the spectralwidth of light that is transmitted through the coloring film CF1 can benarrowed, so that clear display can be provided.

Furthermore, for example, a material that absorbs blue light, greenlight, or red light can be used for the coloring film CF1. Specifically,a material transmitting yellow light, magenta light, or cyan light canbe used for the coloring film CF1. In that case, the spectral width oflight that is absorbed by the coloring film CF1 can be narrowed, so thatbright display can be provided.

«Light-blocking Film BM»

The light-blocking film BM can be formed with a material that preventslight transmission and can thus be used as a black matrix, for example.

Specifically, a resin containing a pigment or dye can be used for thelight-blocking film BM. For example, a resin in which carbon black isdispersed can be used for the light-blocking film.

Alternatively, an inorganic compound, an inorganic oxide, a compositeoxide containing a solid solution of a plurality of inorganic oxides, orthe like can be used for the light-blocking film BM. Specifically, ablack chromium film, a film containing cupric oxide, or a filmcontaining copper chloride or tellurium chloride can be used for thelight-blocking film BM.

«Insulating Film 771»

For example, a material that can be used for the insulating film 521 canbe used for the insulating film 771. The insulating film 771 can beformed of polyimide, an epoxy resin, an acrylic resin, or the like.Alternatively, a film including any of a silicon oxide film, a siliconnitride film, a silicon oxynitride film, and an aluminum oxide film, andthe like, or a film including a material obtained by stacking any ofthese films can be used for the insulating film 771.

«Functional Films 770P and 770D»

An antireflective film, a polarizing film, a retardation film, a lightdiffusion film, a condensing film, or the like can be used for thefunctional film 770P or the functional film 770D, for example.

Specifically, a film containing a dichroic dye can be used for thefunctional film 770P or the functional film 770D. Alternatively, amaterial with a columnar structure having an axis along the directionintersecting a surface of a base can be used for the functional film770P or the functional film 770D. In that case, light can be easilytransmitted in the direction along the axis and easily scattered inother directions.

Alternatively, an antistatic film preventing the attachment of a foreignsubstance, a water repellent film suppressing the attachment of stain, ahard coat film suppressing a scratch in use, or the like can be used asthe functional film 770P.

Specifically, a circularly polarizing film can be used for thefunctional film 770P. Furthermore, a light diffusion film can be usedfor the functional film 770D.

«Second Display Element 550(i,j)»

For example, a display element having a function of emitting light canbe used as the second display element 550(i,j). Specifically, an organicelectroluminescent element, an inorganic electroluminescent element, alight-emitting diode, a quantum-dot LED (QDLED), or the like can be usedas the second display element 550(i,j).

For example, a light-emitting organic compound can be used for the layer553(j) containing a light-emitting material.

For example, quantum dots can be used for the layer 553(j) containing alight-emitting material. Accordingly, the half width becomes narrow, andlight of a bright color can be emitted.

A layered material for emitting blue light, green light, or red lightcan be used for the layer 553(j) containing a light-emitting material,for example.

For example, a belt-like layered material that extends in the columndirection along the signal line S2(j) can be used for the layer 553(j)containing a light-emitting material.

Alternatively, a layered material for emitting white light can be usedfor the layer 553(j) containing a light-emitting material. Specifically,a layered material in which a layer containing a light-emitting materialincluding a fluorescent material that emits blue light, and a layercontaining materials that are other than a fluorescent material and thatemit green light and red light or a layer containing a material that isother than a fluorescent material and that emits yellow light arestacked can be used for the layer 553(j) containing a light-emittingmaterial.

A material that can be used for the wiring or the like can be used forthe electrode 551(i,j), for example.

For example, a material that transmits visible light among the materialsthat can be used for the wiring or the like can be used for theelectrode 551(i,j).

Specifically, conductive oxide, indium-containing conductive oxide,indium oxide, indium tin oxide, indium zinc oxide, zinc oxide, zincoxide to which gallium is added, or the like can be used for theelectrode 551(i,j). Alternatively, a metal film that is thin enough totransmit light can be used as the electrode 551(i,j). Furtheralternatively, a metal film that transmits part of light and reflectsanother part of light can be used for the electrode 551(i,j).Accordingly, the second display element 550(i,j) can have a microcavitystructure. As a result, light of a predetermined wavelength can beextracted more efficiently than light of other wavelengths.

For example, a material that can be used for the wiring or the like canbe used for the electrode 552. Specifically, a material that reflectsvisible light can be used for the electrode 552.

«Driver Circuit GD»

Any of a variety of sequential circuits, such as a shift register, canbe used as a driver circuit GD. For example, a transistor MD, acapacitor, and the like can be used in the driver circuit GD.Specifically, a transistor including a semiconductor film that can beformed in the same process as the semiconductor film of the transistor Mor the transistor that can be used as the switch SW1 can be used.

As the transistor MD, a transistor having a structure different fromthat of the transistor that can be used as the switch SW1 can be used,for example.

Note that the transistor MD can have the same structure as thetransistor M.

«Transistor»

For example, semiconductor films formed in the same process can be usedfor transistors in the driver circuit and the pixel circuit.

As the transistor in the driver circuit or the pixel circuit, abottom-gate transistor or a top-gate transistor can be used, forexample.

For example, a transistor using an oxide semiconductor for asemiconductor film can be used. Specifically, an oxide semiconductorcontaining indium or an oxide semiconductor containing indium, gallium,and zinc can be used for a semiconductor film.

For example, a transistor having a lower leakage current in an off statethan a transistor that uses amorphous silicon for a semiconductor filmcan be used. Specifically, a transistor that uses an oxide semiconductorin a semiconductor film can be used.

Thus, a pixel circuit can hold an image signal for a longer time than apixel circuit including a transistor that uses amorphous silicon for asemiconductor film. Specifically, the selection signal can be suppliedat a frequency of lower than 30 Hz, preferably lower than 1 Hz, morepreferably less than once per minute while flickering is suppressed.Consequently, eyestrain on a user of a data processing device thatincludes the above pixel circuit can be reduced, and power consumptionfor driving can be reduced.

A manufacturing line for a bottom-gate transistor including amorphoussilicon as a semiconductor can be easily remodeled into a manufacturingline for a bottom-gate transistor including an oxide semiconductor as asemiconductor, for example. Furthermore, for example, a manufacturingline for a top-gate transistor including polysilicon as a semiconductorcan be easily remodeled into a manufacturing line for a top-gatetransistor including an oxide semiconductor as a semiconductor. In anyreconstruction, a conventional manufacturing line can be effectivelyused.

For example, a transistor including a semiconductor film 508, aconductive film 504, the conductive film 512A, and the conductive film512B can be used as the switch SW1 (see FIG. 33A). The insulating film506 includes a region positioned between the semiconductor film 508 andthe conductive film 504.

The conductive film 504 includes a region overlapping with thesemiconductor film 508. The conductive film 504 functions as a gateelectrode. The insulating film 506 functions as a gate insulating film.

The conductive films 512A and 512B are electrically connected to thesemiconductor film 508. The conductive film 512A has one of a functionof a source electrode and a function of a drain electrode, and theconductive film 512B has the other.

A transistor including the conductive film 524 can be used as thetransistor in the driver circuit or the pixel circuit (see FIG. 33B).The semiconductor film 508 is positioned between the conductive film 504and a region included in the conductive film 524. The insulating film516 includes a region positioned between the conductive film 524 and thesemiconductor film 508. For example, the conductive film 524 can beelectrically connected to a wiring supplying the same potential as thatsupplied to the conductive film 504.

A conductive film in which a 10-nm-thick film containing tantalum andnitrogen and a 300-nm-thick film containing copper are stacked can beused as the conductive film 504, for example. A film containing copperincludes a region provided such that a film containing tantalum andnitrogen is positioned between the film containing copper and theinsulating film 506.

A material in which a 400-nm-thick film containing silicon and nitrogenand a 200-nm-thick film containing silicon, oxygen, and nitrogen arestacked can be used for the insulating film 506, for example. Note thatthe film containing silicon and nitrogen includes a region provided suchthat the film containing silicon, oxygen, and nitrogen is positionedbetween the film containing silicon and nitrogen and the semiconductorfilm 508.

For example, a 25-nm-thick film containing indium, gallium, and zinc canbe used as the semiconductor film 508.

For example, a conductive film in which a 50-nm-thick film containingtungsten, a 400-nm-thick film containing aluminum, and a 100-nm-thickfilm containing titanium are stacked can be used as the conductive film512A or 512B. Note that the film containing tungsten includes a regionin contact with the semiconductor film 508.

<Structure Example 4 of Display Panel>

A structure of a display panel of one embodiment of the presentinvention is described with reference to FIGS. 39A and 39B.

FIG. 39A and 39B illustrate the structure of the display panel of oneembodiment of the present invention. FIG. 39A is a cross-sectional viewof a pixel, which corresponds to the cross-sectional view taken alongline Y1-Y2 in FIG. 30A. FIG. 39B is a cross-sectional view illustratingpart of the structure of the pixel in FIG. 39A.

The structure of the display panel described in this structure exampleis the same as that of the display panel described with reference toFIGS. 31A and 31B except that a liquid crystal element that can operatein a guest-host liquid crystal mode is used as the first display element750(i,j) and a bottom-gate transistor is used. Different portions willbe described in detail below, and the above description is referred tofor the similar portions.

The display panel described in this embodiment includes a liquid crystalelement that can operate in a guest-host liquid crystal mode as thefirst display element 750(i,j). Thus, a reflective display panel can beobtained without a polarizing plate. Furthermore, an image displayed bythe display panel can be made bright.

«Layer 753 Containing Liquid Crystal Material»

For example, nematic liquid crystal, thermotropic liquid crystal,low-molecular liquid crystal, high-molecular liquid crystal, polymerdispersed liquid crystal, or the like can be used for the layercontaining a liquid crystal material. Alternatively, a liquid crystalmaterial which exhibits a cholesteric phase or the like can be used.Alternatively, a liquid crystal material which exhibits a blue phase canbe used.

Furthermore, a dichroic dye can be used for the layer 753 containing aliquid crystal material. Note that a liquid crystal material containinga dichroic dye is called a guest-host liquid crystal.

Specifically, a material that has high absorbance in the major axisdirection of molecules and low absorbance in the minor-axis directionorthogonal to the major axis direction can be used for the dichroic dye.It is preferable to use a material with a dichroic ratio of 10 orhigher, further preferably 20 or higher for the dichroic dye.

An azo dye, an anthraquinone dye, a dioxazine dye, or the like can beused as the dichroic dye, for example.

Two liquid crystal layers including dichroic dyes having homogeneousalignment that are stacked such that their alignment directions areorthogonal to each other can be used as the layer containing a liquidcrystal material. With the structure, light can be easily absorbed inall directions. Contrast can be increased.

A phase transition guest-host liquid crystal or a structure in which adroplet containing a guest-host liquid crystal is dispersed in a polymercan be used for the layer 753 containing a liquid crystal material.

Note that this embodiment can be combined with any of the otherembodiments in this specification as appropriate.

(Embodiment 7)

In this embodiment, a data processing device to which the display devicedescribed in the above embodiment can be applied is described withreference to FIGS. 40A to 40E and FIGS. 41A to 41E.

FIGS. 40A to 40E and FIGS. 41A to 41E illustrate the structures of thedata processing device of one embodiment of the present invention. FIG.40A is a block diagram of the data processing device, and FIGS. 40B to40E are perspective views illustrating the structures of the dataprocessing device. FIGS. 41A to 41E are perspective views illustratingthe structures of the data processing device.

<Data Processing Device>

A data processing device 5200B described in this embodiment includes anarithmetic device 5210 and an input/output device 5220 (see FIG. 40A).

The arithmetic device 5210 has a function of receiving operation dataand a function of supplying image data on the basis of the operationdata.

The input/output device 5220 includes a display portion 5230, an inputportion 5240, a sensor portion 5250, and a communication portion 5290and has a function of supplying operation data and a function ofreceiving image data. The input/output device 5220 also has a functionof supplying sensing data, a function of supplying communication data,and a function of receiving communication data.

The input portion 5240 has a function of supplying operation data. Forexample, the input portion 5240 supplies operation data on the basis ofoperation by the user of the data processing device 5200B.

Specifically, a keyboard, a hardware button, a pointing device, a touchsensor, an audio input device, a viewpoint input device, or the like canbe used as the input portion 5240.

The display portion 5230 includes a display panel and has a function ofdisplaying image data. For example, the display device 50 described inthe above embodiment can be used for the display portion 5230.

The sensor portion 5250 has a function of supplying sensing data. Forexample, the sensor portion 5250 has a function of sensing a surroundingenvironment where the data processing device is used and supplyingsensing data.

Specifically, an illuminance sensor, an imaging device, an attitudedetermination device, a pressure sensor, a human motion sensor, or thelike can be used as the sensor portion 5250.

The communication portion 5290 has a function of receiving and supplyingcommunication data. For example, the communication portion 5290 has afunction of being connected to another electronic device or acommunication network by wireless communication or wired communication.Specifically, the communication portion 5290 has a function of localarea wireless communication, telephone communication, or near fieldwireless communication, for example.

«Structural Example 1 of Data Processing Device»

For example, the display portion 5230 can have an outer shape along acylindrical column or the like (see FIG. 40B). Furthermore, the displayportion 5230 has a function of changing a displaying method inaccordance with the illuminance of a usage environment and a function ofchanging displayed contents when sensing the existence of a person.Thus, the data processing device can be mounted on a column of abuilding, for example. Alternatively, the data processing device candisplay advertisement, information, or the like. The data processingdevice can be used for a digital signage or the like.

«Structural Example 2 of Data Processing Device»

For example, the data processing device has a function of generatingimage data on the basis of the path of a pointer used by a user (seeFIG. 40C). Specifically, it is possible to use a display panel with adiagonal of 20 inches or more, preferably 40 inches or more, furtherpreferably 55 inches or more. Alternatively, display panels can bearranged in one display region. Alternatively, display panels can bearranged to be used as a multiscreen. In this case, the data processingdevice can be used for an electronic blackboard, an electronic bulletinboard, a digital signage, or the like.

«Structural Example 3 of Data Processing Device»

For example, the data processing device has a function of changing adisplaying method in accordance with the illuminance of a usageenvironment (see FIG. 40D). Thus, it is possible to obtain a smartwatchwith reduced power consumption, for example. Alternatively, it ispossible to obtain a smartwatch that can display an image such that thesmartwatch is favorably used even in an environment with intenseexternal light, e.g., in the open air under fine weather.

«Structural Example 4 of Data Processing Device»

The display portion 5230 has a surface gently curved along a sidesurface of a housing (see FIG. 40E). The display portion 5230 includes adisplay panel that has, for example, a function of performing display ona front surface, side surfaces, and a top surface. Thus, it is possibleto obtain a mobile phone that can display image data on not only itsfront surface but also its side surfaces and top surface.

«Structural Example 5 of Data Processing Device»

For example, the data processing device has a function of changing adisplaying method in accordance with the illuminance of a usageenvironment (see FIG. 41A). Thus, it is possible to obtain a smartphonewith reduced power consumption. Alternatively, it is possible to obtaina smartphone that can display an image such that the smartphone isfavorably used even in an environment with intense external light, e.g.,in the open air under fine weather.

«Structural Example 6 of Data Processing Device»

For example, the data processing device has a function of changing adisplaying method in accordance with the illuminance of a usageenvironment (see FIG. 41B). Thus, it is possible to obtain a televisionsystem that can display an image such that the television system isfavorably used even when exposed to intense external light poured into aroom in a sunny day.

«Structural Example 7 of Data Processing Device»

For example, the data processing device has a function of changing adisplaying method in accordance with the illuminance of a usageenvironment (see FIG. 41C). Thus, it is possible to obtain a tabletcomputer that can display an image such that the tablet computer isfavorably used even in an environment with intense external light, e.g.,in the open air under fine weather.

«Structural Example 8 of Data Processing Device»

For example, the data processing device has a function of changing adisplaying method in accordance with the illuminance of a usageenvironment (see FIG. 41D). Thus, it is possible to obtain a digitalcamera that can display a subject such that an image is favorably viewedeven in an environment with intense external light, e.g., in the openair under fine weather.

«Structural Example 9 of Data Processing Device»

For example, the data processing device has a function of changing adisplaying method in accordance with the illuminance of a usageenvironment (see FIG. 41E). Thus, it is possible to obtain a personalcomputer that can display an image such that the personal computer isfavorably used even in an environment with intense external light, e.g.,in the open air under fine weather.

Note that this embodiment can be combined with any of the otherembodiments in this specification as appropriate.

For example, in this specification and the like, an explicit description“X and Y are connected” means that X and Y are electrically connected, Xand Y are functionally connected, and X and Y are directly connected.Accordingly, another element may be provided between elements having aconnection relation illustrated in drawings and texts, without beinglimited to a predetermined connection relation, for example, theconnection relation illustrated in the drawings and the texts.

Here, X and Y each denote an object (e.g., a device, an element, acircuit, a wiring, an electrode, a terminal, a conductive film, and alayer).

Examples of the case where X and Y are directly connected include thecase where an element that allows an electrical connection between X andY (e.g., a switch, a transistor, a capacitor, an inductor, a resistor, adiode, a display element, a light-emitting element, and a load) is notconnected between X and Y, and the case where X and Y are connectedwithout the element that allows the electrical connection between X andY provided therebetween.

For example, in the case where X and Y are electrically connected, oneor more elements that enable electrical connection between X and Y(e.g., a switch, a transistor, a capacitor, an inductor, a resistor, adiode, a display element, a light-emitting element, or a load) can beconnected between X and Y. A switch is controlled to be on or off. Thatis, a switch is conducting or not conducting (is turned on or off) todetermine whether current flows therethrough or not. Alternatively, theswitch has a function of selecting and changing a current path. Notethat the case where X and Y are electrically connected includes the casewhere X and Y are directly connected.

For example, in the case where X and Y are functionally connected, oneor more circuits that enable functional connection between X and Y(e.g., a logic circuit such as an inverter, a NAND circuit, or a NORcircuit; a signal converter circuit such as a DA converter circuit, anAD converter circuit, or a gamma correction circuit; a potential levelconverter circuit such as a power supply circuit (e.g., a step-upcircuit or a step-down circuit) or a level shifter circuit for changingthe potential level of a signal; a voltage source; a current source; aswitching circuit; an amplifier circuit such as a circuit that canincrease signal amplitude, the amount of current, or the like, anoperational amplifier, a differential amplifier circuit, a sourcefollower circuit, or a buffer circuit; a signal generation circuit; amemory circuit; and/or a control circuit) can be connected between X andY. Note that for example, in the case where a signal output from X istransmitted to Y even when another circuit is provided between X and Y,X and Y are functionally connected. Note that the case where X and Y arefunctionally connected includes the case where X and Y are directlyconnected and the case where X and Y are electrically connected.

Note that in this specification and the like, an explicit description “Xand Y are electrically connected” means that X and Y are electricallyconnected (i.e., the case where X and Y are connected with anotherelement or another circuit provided therebetween), X and Y arefunctionally connected (i.e., the case where X and Y are functionallyconnected with another circuit provided therebetween), and X and Y aredirectly connected (i.e., the case where X and Y are connected withoutanother element or another circuit provided therebetween). That is, inthis specification and the like, the explicit description “X and Y areelectrically connected” is the same as the description “X and Y areconnected”.

Note that, for example, the case where a source (or a first terminal orthe like) of a transistor is electrically connected to X through (or notthrough) Z1 and a drain (or a second terminal or the like) of thetransistor is electrically connected to Y through (or not through) Z2,or the case where a source (or a first terminal or the like) of atransistor is directly connected to one part of Z1 and another part ofZ1 is directly connected to X while a drain (or a second terminal or thelike) of the transistor is directly connected to one part of Z2 andanother part of Z2 is directly connected to Y, can be expressed by usingany of the following expressions.

Examples of the expressions include, “X Y, a source (or a first terminalor the like) of a transistor, and a drain (or a second terminal or thelike) of the transistor are electrically connected to each other, and X,the source (or the first terminal or the like) of the transistor, thedrain (or the second terminal or the like) of the transistor, and Y areelectrically connected to each other in this order”, “a source (or afirst terminal or the like) of a transistor is electrically connected toX, a drain (or a second terminal or the like) of the transistor iselectrically connected to Y, and X, the source (or the first terminal orthe like) of the transistor, the drain (or the second terminal or thelike) of the transistor, and Y are electrically connected to each otherin this order”, and “X is electrically connected to Y through a source(or a first terminal or the like) and a drain (or a second terminal orthe like) of a transistor, and X, the source (or the first terminal orthe like) of the transistor, the drain (or the second terminal or thelike) of the transistor, and Y are provided to be connected in thisorder”. When the connection order in a circuit structure is defined byan expression similar to the above examples, a source (or a firstterminal or the like) and a drain (or a second terminal or the like) ofa transistor can be distinguished from each other to specify thetechnical scope.

Other examples of the expressions include, “a source (or a firstterminal or the like) of a transistor is electrically connected to Xthrough at least a first connection path, the first connection path doesnot include a second connection path, the second connection path is apath between the source (or the first terminal or the like) of thetransistor and a drain (or a second terminal or the like) of thetransistor, Z1 is on the first connection path, the drain (or the secondterminal or the like) of the transistor is electrically connected to Ythrough at least a third connection path, the third connection path doesnot include the second connection path, and Z2 is on the thirdconnection path”. It is also possible to use the expression “a source(or a first terminal or the like) of a transistor is electricallyconnected to X through at least Z1 on a first connection path, the firstconnection path does not include a second connection path, the secondconnection path includes a connection path through the transistor, adrain (or a second terminal or the like) of the transistor iselectrically connected to Y through at least Z2 on a third connectionpath, and the third connection path does not include the secondconnection path”. Still another example of the expression is “a source(or a first terminal or the like) of a transistor is electricallyconnected to X through at least Z1 on a first electrical path, the firstelectrical path does not include a second electrical path, the secondelectrical path is an electrical path from the source (or the firstterminal or the like) of the transistor to a drain (or a second terminalor the like) of the transistor, the drain (or the second terminal or thelike) of the transistor is electrically connected to Y through at leastZ2 on a third electrical path, the third electrical path does notinclude a fourth electrical path, and the fourth electrical path is anelectrical path from the drain (or the second terminal or the like) ofthe transistor to the source (or the first terminal or the like) of thetransistor”. When the connection path in a circuit structure is definedby an expression similar to the above examples, a source (or a firstterminal or the like) and a drain (or a second terminal or the like) ofa transistor can be distinguished from each other to specify thetechnical scope.

Note that one embodiment of the present invention is not limited tothese expressions which are just examples. Here, X, Y, Z1, and Z2 eachdenote an object (e.g., a device, an element, a circuit, a wiring, anelectrode, a terminal, a conductive film, and a layer).

Even when independent components are electrically connected to eachother in a circuit diagram, one component has functions of a pluralityof components in some cases. For example, when part of a wiring alsofunctions as an electrode, one conductive film functions as the wiringand the electrode. Thus, “electrical connection” in this specificationincludes in its category such a case where one conductive film hasfunctions of a plurality of components.

(Embodiment 8)

<Composition of CAC-OS>

The composition of a CAC-OS that can be used for a transistor disclosedin one embodiment of the present invention is described below.

The CAC-OS has, for example, a composition in which elements included inan oxide semiconductor are unevenly distributed. Materials includingunevenly distributed elements each have a size of greater than or equalto 0.5 nm and less than or equal to 10 nm, preferably greater than orequal to 1 nm and less than or equal to 2 nm, or a similar size. Notethat in the following description of an oxide semiconductor, a state inwhich one or more metal elements are unevenly distributed and regionsincluding the metal element(s) are mixed is referred to as a mosaicpattern or a patch-like pattern. The region has a size of greater thanor equal to 0.5 nm and less than or equal to 10 nm, preferably greaterthan or equal to 1 nm and less than or equal to 2 nm, or a similar size.

Note that an oxide semiconductor preferably contains at least indium. Inparticular, indium and zinc are preferably contained. In addition,aluminum, gallium, yttrium, copper, vanadium, beryllium, boron, silicon,titanium, iron, nickel, germanium, zirconium, molybdenum, lanthanum,cerium, neodymium, hafnium, tantalum, tungsten, magnesium, and the likemay be contained.

For example, of the CAC-OS, an In—Ga—Zn oxide with the CAC composition(such an In—Ga—Zn oxide may be particularly referred to as CAC-IGZO) hasa composition in which materials are separated into indium oxide(InO_(X1), where X1 is a real number greater than 0) or indium zincoxide (In_(X2)Zn_(Y2)O_(Z2), where X2, Y2, and Z2 are real numbersgreater than 0), and gallium oxide (GaO_(X3), where X3 is a real numbergreater than 0), gallium zinc oxide (Ga_(X4)Zn_(Y4)O_(Z4), where X4, Y4,and Z4 are real numbers greater than 0), or the like, and a mosaicpattern is formed. Then, InO_(X1) or In_(X2)Zn_(Y2)O_(Z2) forming themosaic pattern is evenly distributed in the film. This composition isalso referred to as a cloud-like composition.

That is, the CAC-OS is a composite oxide semiconductor with acomposition in which a region including GaO_(X3) as a main component anda region including In_(X2)Zn_(Y2)O_(Z2) or InO_(X1) as a main componentare mixed. Note that in this specification, for example, when the atomicratio of In to an element M in a first region is greater than the atomicratio of In to the element M in a second region, the first region hashigher. In concentration than the second region.

Note that a compound including In, Ga, Zn, and O is also known as IGZO.Typical examples of IGZO include a crystalline compound represented byInGaO₃(ZnO)_(m1) (m1 is a natural number) and a crystalline compoundrepresented by In_((1+x0))Ga_((1−x0))O₃(ZnO)_(m0)(−1≤x0≤1; m0 is a givennumber).

The above crystalline compounds have a single crystal structure, apolycrystalline structure, or a c-axis-aligned crystalline oxidesemiconductor or c-axis aligned and a-b-plane anchored crystalline oxidesemiconductor (CAAC) structure. Note that the CAAC structure is acrystal structure in which a plurality of IGZO nanocrystals have c-axisalignment and are connected in the a-b plane direction withoutalignment.

On the other hand, the CAC-OS relates to the material composition of anoxide semiconductor. In a material composition of a CAC-OS including In,Ga, Zn, and O, nanoparticle regions including Ga as a main component areobserved in part of the CAC-OS and nanoparticle regions including In asa main component are observed in part thereof. These nanoparticleregions are randomly dispersed to form a mosaic pattern. Therefore, thecrystal structure is a secondary element for the CAC-OS.

Note that in the CAC-OS, a stacked-layer structure including two or morefilms with different atomic ratios is not included. For example, atwo-layer structure of a film including In as a main component and afilm including Ga as a main component is not included.

A boundary between the region including GaO_(X3) as a main component andthe region including In_(X2)Zn_(Y2)O_(Z2) or InO_(X1) as a maincomponent is not clearly observed in some cases.

In the case where one or more of aluminum, yttrium, copper, vanadium,beryllium, boron, silicon, titanium, iron, nickel, germanium, zirconium,molybdenum, lanthanum, cerium, neodymium, hafnium, tantalum, tungsten,magnesium, and the like are contained instead of gallium in a CAC-OS,nanoparticle regions including the selected metal element(s) as a maincomponent(s) are observed in part of the CAC-OS and nanoparticle regionsincluding In as a main component are observed in part thereof, and thesenanoparticle regions are randomly dispersed to form a mosaic pattern inthe CAC-OS.

The CAC-OS can be formed by a sputtering method under conditions where asubstrate is not heated intentionally, for example. In the case offorming the CAC-OS by a sputtering method, one or more selected from aninert gas (typically, argon), an oxygen gas, and a nitrogen gas may beused as a deposition gas. The ratio of the flow rate of an oxygen gas tothe total flow rate of the deposition gas at the time of deposition ispreferably as low as possible, and for example, the flow ratio of anoxygen gas is preferably higher than or equal to 0% and less than 30%,further preferably higher than or equal to 0% and less than or equal to10%.

The CAC-OS is characterized in that no clear peak is observed inmeasurement using θ/2θ scan by an out-of-plane method, which is an X-raydiffraction (XRD) measurement method. That is, X-ray diffraction showsno alignment in the a-b plane direction and the c-axis direction in ameasured region.

In an electron diffraction pattern of the CAC-OS which is obtained byirradiation with an electron beam with a probe diameter of 1 nm (alsoreferred to as a nanometer-sized electron beam), a ring-like region withhigh luminance and a plurality of bright spots in the ring-like regionare observed. Therefore, the electron diffraction pattern indicates thatthe crystal structure of the CAC-OS includes a nanocrystal (nc)structure with no alignment in plan-view and cross-sectional directions.

For example, an energy dispersive X-ray spectroscopy (EDX) mapping imageconfirms that an In—Ga—Zn oxide with the CAC composition has a structurein which a region including GaO_(X3) as a main component and a regionincluding In_(X2)Zn_(Y2)O_(Z2) or InO_(X1) as a main component areunevenly distributed and mixed.

The CAC-OS has a structure different from that of an IGZO compound inwhich metal elements are evenly distributed, and has characteristicsdifferent from those of the IGZO compound. That is, in the CAC-OS,regions including GaO_(X3) or the like as a main component and regionsincluding In_(X2)Zn_(Y2)O_(Z2) or InO_(X1) as a main component areseparated to form a mosaic pattern.

The conductivity of a region including In_(X2)Zn_(Y2)O_(Z2) or InO_(X1)as a main component is higher than that of a region including GaO_(X3)or the like as a main component. In other words, when carriers flowthrough regions including In_(X2)Zn_(Y2)O_(Z2) or InO_(X1) as a maincomponent, the conductivity of an oxide semiconductor is exhibited.Accordingly, when regions including In_(X2)Zn_(Y2)O_(Z2) or InO_(X1) asa main component are distributed in an oxide semiconductor like a cloud,high field-effect mobility (μ) can be achieved.

In contrast, the insulating property of a region including GaO_(X3) orthe like as a main component is higher than that of a region includingIn_(X2)Zn_(Y2)O_(Z2) or InO_(X1) as a main component. In other words,when regions including GaO_(X3) or the like as a main component aredistributed in an oxide semiconductor, leakage current can be suppressedand favorable switching operation can be achieved.

Accordingly, when a CAC-OS is used for a semiconductor element, theinsulating property derived from GaO_(X3) or the like and theconductivity derived from In_(X2)Zn_(Y2)O_(Z2) or InO_(X1) complementeach other, whereby high on-state current (I_(on)) and high field-effectmobility (μ) can be achieved.

A semiconductor element including a CAC-OS has high reliability. Thus,the CAC-OS is suitably used in a variety of semiconductor devicestypified by a display.

At least part of this embodiment can be implemented in combination withany of the other embodiments and the other examples described in thisspecification as appropriate.

EXAMPLE

In this example, the display unit 60 described in Embodiment 1 wasfabricated and its power consumption was measured.

In this example, the display unit 60 including a reflective element anda light-emitting element in the pixel 10 was fabricated. FIG. 42 is aschematic view of the fabricated display unit.

The display unit 60 illustrated in FIG. 42 includes a substrate 251, thepixel array 61, the gate driver 62, the gate driver 63, the sourcedriver IC 64, a wiring 258, and an FPC 252.

FIG. 42 illustrates an enlarged view of part of the pixel array 61. Inthe pixel array 61, electrodes 216R are arranged in matrix. Theelectrode 216R has a function of reflecting visible light 241, andserves as a reflective electrode of a reflective element.

As illustrated in FIG. 42, the electrode 216R includes an opening 240.In addition, the display unit 60 includes a light-emitting element 217that is positioned closer to the substrate 251 than the electrode 216R.Light 242 emitted from the light-emitting element 217 is extracted outthrough the opening 240.

The display unit 60 has three display modes: a mode in which an image isdisplay only by the reflective element (a reflective mode), a mode inwhich an image is displayed only by the light-emitting element (alight-emitting mode), and a mode in which an image is displayed by acombination of the reflective element and the light-emitting element (ahybrid mode).

Hybrid mode is a method for displaying a letter or an image usingreflected light and self-emitted light together in one panel thatcomplement the color tone or light intensity of each other.Alternatively, a hybrid mode is a method for displaying a letter and/oran image using light from the reflective element and the light-emittingelement in one pixel or one subpixel. Note that when a hybrid displayperforming hybrid display is locally observed, a pixel or a subpixelperforming display using one of the reflective element and thelight-emitting element and a pixel or a subpixel performing displayusing both of the reflective element and the light-emitting element areincluded in some cases.

Note that in this specification and the like, hybrid display satisfiesany one or a plurality of the above-described descriptions.

Furthermore, a hybrid display includes a plurality of display elementsin one pixel or one subpixel. Note that as an example of the pluralityof display elements, a reflective element that reflects light and alight-emitting element that emits light can be given. Note that thereflective element and the light-emitting element can be controlledindependently. A hybrid display has a function of displaying a letterand/or an image using one or both of reflected light and self-emittedlight in a display portion.

In this example, a reflective liquid crystal element (hereinafter,referred to as a liquid crystal element) was used as the reflectiveelement, and an organic EL element (hereinafter, referred to as an ELelement) was used as the light-emitting element 217.

FIGS. 43A to 43F are photographs showing the appearance of thefabricated display unit.

FIG. 43A shows the case where all the liquid crystal elements and allthe EL elements included in a pixel array display black. In other words,all the EL elements stop light emission.

FIGS. 43B to 43F each show the case where all the EL elements displaywhite and all the liquid crystal elements display black. The emissionintensity of the EL elements is gradually changed from FIG. 43B to FIG.43F.

FIGS. 43B, 43C, 43D, 43E and 43F are photographs showing the case wherethe luminance is 1.3 cd/m², 10.5 cd/m², 28.2 cd/m², 56.3 cd/m², and 92.4cd/m², respectively.

Measurement results of power consumption of the display unit in each ofFIGS. 43A to 43F are shown in FIGS. 44A and 44B.

A to F in graphs of FIGS. 44A and 44B correspond to the powerconsumption in FIGS. 43A to 43F, respectively. Each bar graph of thefigures shows power consumption of the EL element (EL), powerconsumption of a source driver (SD), power consumption of a gate driverdriving the liquid crystal element (GD(LC)), and power consumption of agate driver driving the EL element (GD(EL)).

FIG. 44A shows power consumption in the case where the display unit wasdriven at 60 Hz and FIG. 44B shows power consumption in the case whereboth of the liquid crystal element and the EL element performed the IDSdriving.

As the luminance of the display unit became higher (the emissionintensity of the EL element became higher), power consumption was alsoincreased in both FIGS. 44A and 44B.

Comparison between FIGS. 44A and 44B indicates that the powerconsumption of the source driver, the gate driver driving the liquidcrystal element, and the gate driver driving the EL element can besignificantly reduced by performing the IDS driving.

FIGS. 45A to 45E are photographs showing the appearance of thefabricated display unit.

FIG. 45A shows the case where a color image of a butterfly is displayedin the above-described hybrid mode.

FIG. 45B shows the case where a color image of a flower is displayed inthe above-described hybrid mode.

FIG. 45C shows the case where text (letters) and a picture are displayedin the above-described reflective mode. The image in FIG. 45C isdisplayed with two colors (black and white).

FIG. 45D shows the case where a highlight emphasizing the text is addedto the image in FIG. 45C. A highlight (color) displayed by the ELelement is added to the image (black and white) displayed by the liquidcrystal element.

FIG. 45E shows the case where a highlight emphasizing the text is addedto the image in FIG. 45C. A highlight (color) displayed by the ELelement is added to the image (black and white) displayed by the liquidcrystal element. FIG. 45E is different from FIG. 45D in that the numberof the highlights is larger than that in FIG. 45D, that is, the numberof the EL elements emitting light is larger than that in FIG. 45D.

Measurement results of power consumption of the display unit in each ofFIGS. 45A to 45E are shown in FIGS. 46A and 46B.

A to E of graphs of FIGS. 46A and 46B correspond to the powerconsumption in FIGS. 45A to 45E, respectively. As in FIGS. 44A and 44B,each bar graph of the figures shows power consumption of the EL element(EL), power consumption of a source driver (SD), power consumption of agate driver driving the liquid crystal element (GD(LC)), and powerconsumption of a gate driver driving the EL element (GD(EL)).

FIG. 46A shows power consumption in the case where the display unit wasdriven at 60 Hz and FIG. 46B shows power consumption in the case whereboth of the liquid crystal element and the EL element performed the IDSdriving.

Comparison between FIGS. 46A and 46B indicates that the powerconsumption of the source driver, the gate driver driving the liquidcrystal element, and the gate driver driving the EL element can besignificantly reduced by performing the IDS driving. In particular, inthe case where the text is displayed by the liquid crystal element(FIGS. 45C to 45E), power consumption of the entire display unitincluding the liquid crystal element and the EL element can be reducedto 50 mW or smaller.

It is found from this example that the power consumption of the entiredisplay unit can be significantly reduced when both of the EL elementand the liquid crystal element perform the IDS driving.

REFERENCE NUMERALS

10: pixel, 10 a: pixel, 10 b: pixel, 10 c: pixel, 50: display device,60: display unit, 61: pixel array, 62: gate driver, 63: gate driver, 64:source driver IC, 64 a: source driver IC, 64 d: source driver IC, 70:touch sensor unit, 71: sensor array, 72: touch sensor IC, 80:application processor, 90: tablet information terminal, 91: displayregion, 92: illustration, 93: frame, 94: frame, 95: stylus, 100:circuit, 101: transistor, 109: transistor, 110: circuit, 111:transistor, 113: transistor, 120: circuit, 121: transistor, 123:transistor, 216R: electrode, 217: light-emitting element, 240: opening,241: visible light, 242: light, 251: substrate, 252: FPC, 258: wiring,301: transistor, 302: node, 303: capacitor, 304: liquid crystal element,310: capacitor, 311: transistor, 312: transistor, 313: transistor, 314:light-emitting element, 315: node, 402: driving circuit, 403: detectioncircuit, 404: capacitor, 411: substrate, 412: substrate, 413: FPC, 414:wiring, 420: liquid crystal element, 421: electrode, 421 a: electrode,421 b: electrode, 422: electrode, 422 a: electrode, 422 b: electrode,423: liquid crystal, 424: insulating film, 431: coloring film, 441:electrode, 441 a: electrode, 441 b: electrode, 443: FPC, 463: ELelement, 464: electrode, 465: EL layer, 466: electrode, 475: sensingelement, 501B: insulating film, 501C: insulating film, 504: conductivefilm, 505: bonding layer, 506: insulating film, 508: semiconductor film,511B: conductive film, 512A: conductive film, 512B: conductive film,516: insulating film, 518: insulating film, 518A: insulating film,518A1: insulating film, 518A2: insulating film, 518B: insulating film,519B: terminal, 520: functional layer, 521: insulating film, 521A:insulating film, 521B: insulating film, 521C: insulating film, 522:connection portion, 524: conductive film, 528: insulating film, 530:pixel circuit, 550: display element, 551: electrode, 552: electrode,553: layer, 560: optical element, 560A: region, 560B: region, 560C:region, 565: covering film, 570: substrate, 591A: opening, 592B:opening, 601: transistor, 602: transistor, 610: electrode, 611:electrode, 612: semiconductor layer, 616: electrode, 617: electrode,621: insulating layer, 622: insulating layer, 624: insulating layer,625: electrode, 626: anisotropic conductive layer, 627: sealant, 628:filler, 629: insulating layer, 630: light-blocking film, 631: alignmentfilm, 632: alignment film, 633: spacer, 634: wiring, 654: anisotropicconductive layer, 661: partition wall, 662: wiring, 663: insulatinglayer, 700: display unit, 702: pixel, 703: pixel, 705: sealant, 720:functional layer, 750: display element, 751: electrode, 751B: reflectivefilm, 751H: region, 752: electrode, 753: layer, 770: substrate, 770B:bonding layer, 770D: functional film, 770P: functional film, 770PA:functional film, 770PB: functional film, 771: insulating film, 771A:insulating film, 771B: insulating film, 801: control circuit, 802:driver, 803: frame memory, 804: frame memory, 806: gate driver signalgeneration circuit, 807: gate driver signal generation circuit, 810:timing controller, 5200B: data processing device, 5210: arithmeticdevice, 5220: input/output device, 5230: display portion, 5240: inputportion, 5250: sensor portion, and 5290: communication portion.

This application is based on Japanese Patent Application Serial No.2016-207318 filed with Japan Patent Office on Oct. 21, 2016, JapanesePatent Application Serial No. 2016-207335 filed with Japan Patent Officeon Oct. 21, 2016, and Japanese Patent Application Serial No. 2016-210464filed with Japan Patent Office on Oct. 27, 2016, the entire contents ofwhich are hereby incorporated by reference.

The invention claimed is:
 1. A method for driving a display devicecomprising: the display device comprising pixels, a gate driver, and atouch sensor unit, the method comprising the steps of: detecting, by thetouch sensor unit, pixels touched by a user, and supplying, by the gatedriver, a signal to a row including the detected pixels during a frameperiod, wherein a signal is not supplied to a row not including thedetected pixels during the entirety of the frame period, and wherein thetouch sensor unit stops detecting a touch during supplying the signal tothe row.
 2. The method for driving the display device according to claim1, wherein the pixels each comprise a transistor comprising a metaloxide in a channel formation region.
 3. A method for driving a displaydevice comprising pixels, a gate driver, and a touch sensor unit, themethod comprising the steps of: detecting, by the touch sensor unit,pixels touched by a user, and supplying, by the gate driver, a signal toa row including the detected pixels during a frame period, wherein asignal is not supplied to a row not including the detected pixels duringthe entirety of the frame period, wherein the touch sensor unit stopsdetecting a touch during supplying the signal to the row, and whereinthe pixel comprises a reflective element and a light-emitting element.4. The method for driving a display device according to claim 3, whereinthe pixels each comprise a transistor comprising a metal oxide in achannel formation region.